The Hamilton 992B Railroad Pocket Watch, Hamilton Railway Special

Hamilton Watch, the watch of railroad accuracy

The Hamilton grade 992B is a high quality antique mechanical pocket watch. A well maintained and adjusted watch kept in a fixed location at room temperature can reach accuracies normally only seen with quartz watches. If you use it and the watch is exposed to different temperatures and shaken or turned then you will achieve about +/- 15sec accuracy per week. A lot of other mechanical watches are off that much in just one day.

train

The need for Railroad Watches to be "railroad approved" stemmed from a number of train accidents in the late 1800's where two trains collided head on due to poor time keeping. Regular watch inspection and consistent time keeping was the only thing that kept trains from running into each other on Americas single track railways. These railways had a single track for both directions and two trains running in opposite direction could pass each other at railway stations and other places which had two tracks, one for each direction, for a short distance only.

A notable watch inspector was Webb C. Ball. His first job as a time inspector was when he was brought in by the Lake Shore and Michigan Southern Railways in 1891 after a crash and was tasked with bringing their time inspection system up to industry standards. Ball's career eventually led to him being the time inspector on more than half the United States' railways, leading to a far more uniform set of standards across the US. He gave a very interessting interview in the New-York Tribune January 16, 1910 (Many lives sacrificed because of faulty watches, interview with Webb C. Ball January 16, 1910).

An interesting question from a historic point of view is of course: why did nobody in North America come up with any solution other than time keeping? Many other countries solved the root cause of the problem with station to station communication, signaling, tokens or dual track. In this article we focus however on watches and it is this focus on timing only that lead to those beautiful and precise American railroad watches.

The Hamilton 992B pocket watch is a beautiful watch not only on the outside. It has a beautifully decorated movement.

A 1948 Hamilton Railway Special, grade 992B, 21J

Hamilton 992B technical specifications

Movement size: 16, 1.700 inches, 43.18 mm diameter
Approximate watch size (depends on case): 2 inch (5cm) diameter, weight 90g
Jewels (gemstone bearings): 21, friction set, all upper jewel settings are gold
Rate: 2.5Hz, 5 beats per second, 18000 bph (beats per hour)
The watch runs about 52 hours when fully wound
Balance wheel: Aurium, a monometallic beryllium-silver-nickel alloy, Aurium is a Hamilton marketing term (trademarked in April 1940 by Hamilton), the exact composition of the alloy was kept secret.
Balance staff: friction fit, no rivet.
Hair spring material: Elinvar-Extra
Adjustement: temperature, isochronism and 6 positions

Position adjustment refers to the mechanical design of the balance wheel and the hairspring. The little weights on the balance wheel are an important part of that adjustment. It is done to maintain approximately the same rate of balance wheel oscillation, regardless of which of the specified positions the watch is in. The 6 positions are: (1) dial up, (2) dial down, (3) stem up, (4) stem at 9 o'clock and (5) stem at 3 o'clock, (6) stem down at the 6 o'clock.
It's the positional adjustment and the temperature adjustment that sets this watch apart from many others made in the 1940's.
Adjustment for isochronism means that the watch runs with the same rate independent of whether the watch if fully wound or almost unwound.
Hamilton had in the 1920's a sales and marketing brochure called the Timekeeper and it had a chapter explaining those adjustments: hamilton_adjustments.pdf, 238794 bytes

Dial material: a few models had porcelain enamel (aka vitreous enamel) on brass but most are made of a melamine resin (plastic) coated brass plate.

Melamine resin (melamine formaldehyde) was one of the first widely used plastics. It's the stuff you find on old light switches or old electrical sockets. It's a very hard and brittle plastic. It does not easily burn and is very resistant to chemicals. The melamine resin dials do usually have cracks and hairlines after a few decades. The enamel dials may get hairlines too but generally not as big ones as the melamine dials. I have seen some cases where people have removed the original melamine and completely re-painted the dial. It looks nice but it is not original and Hamilton did not use such "paint on brass" dials for the 992b.

Hamilton 992B cases and dials

992b is the movement and you could have it with different dials and cases.
The term "Railway Special", as found on most Hamilton 992B watches, is a registered trademark of Hamilton.

I am not sure why most Hamilton 992B watches had the words "Hamilton Railway Special" on the dial while a few had just the word "Hamilton" on the dial.

Hamilton pocket watch movement parts

The following picture shows an exploded view of a Hamilton size 16 pocket watch. This picture can be useful during service and maintenance and when you need to know the names of the watch parts.

Exploded view of a Hamilton pocket watch movement (click here for a printable PDF version)

Regulating the Hamilton 992B (adjusting the speed or rate)

The Hamilton 992B regulator is adjusted not with a simple "F - S" lever, but with a spring loaded micrometer screw that adjusts the regulator far more precisely. One full turn of the precision regulator screw changes the rate of the 992B by about 18 to 22 seconds per day.

You need a very small watch maker screw driver to adjust the regulator. Use the watch for at least a week before you change anything. Talk to a watchmaker if you are not comfortable doing this. You don't want to ruin your watch.

The Hamilton 992B has far less temperature dependencies than many other mechanical pocket watches from the railroad area but there is still a little temperature dependency and of course a positional dependency. The Hamilton 992b is adjusted to 6 positions but there is still a noticeable difference between running in horizontal position and running in upright position. Hamilton tried to minimize the positional dependency but it can't really do anything about the basic laws of physics. Hamilton was very good at marketing and advertising their watches. The 992b was however in reality not much better than any other high end pocket watch made around the same time.

A mechanical watch runs a little faster when it is steady in horizontal position on the desk and a little slower in vertical position. This is because the rate at which the balance oscillates depends on the amplitude (how far it swings around) and the balance wheel (and all the other wheels) are experiencing friction on both ends of the pivots in vertical position. This reduces the amplitude a bit and lowers the rate at which the watch is running in vertical position compared to horizontal position (all wheels are experiencing only friction on one pivot in horizontal position). In other words the rate depends on how you carry the watch. Hamilton published in 1951 a technical note that explains regulation nicely. Click on the picture for a PDF version of the document:

Hamilton tech. note on regulation (PDF, 1031997 bytes)

The Hamilton 992b precision regulator screw

A modern timegrapher can be helpful when you regulate a 992b but it is not absolutely required since the 992b has a regulator screw and one full turn on the screw changes the rate by about 20sec a day. If you want to change the rate by a given daily rate then you can simply calculate by how many degrees you have to turn the regulator screw.

A timegrapher (or timing machine) is a machine that listens to the various "click events" that a mechanical watch produces and it times those events. It can be used to check instantly if the watch movement is running well.
I don't know what the lift angle of the Hamilton 992b really is but if you set it on the timegrapher to 52° then you can expect an amplitude of just over 250° in horizontal position. I have never seen a 992b that had amplitude higher than 300°. This may seem like a low amplitude to those familiar with timegraphers and swiss movements. I don't know why the 992b has a relatively low amplitude but it is normal. Hamilton 992 watches (without the b) and old steel springs can have amplitudes above 300°.

A Hamilton 992b mounted with a movement holder on a timegrapher

Timegrapher readings from an average Hamilton 992b. It's normal for a 992b to have only an amplitude in the 250° range. A beat error of 2ms is at the upper limit of what is acceptable.
Update March 2020: Bruce Ellison contacted me to let me know that the low amplitude is actually due to an incorrect setting on the timing machine. The lift angle should be set on the timing machine to 44 degrees for all Hamilton 992b watches and then it should show an amplitude of at least 270-290 degrees.

Timegrapher readings from a very good Hamilton 992b. The amplitude is still only 263°
The distance between the lines drawn by the timegrapher corresponds to the beat error. That is: the beat error is difference between a balance swing to the left and one to the right. It would be zero if the roller jewel was in idle position exactly in the middle between the banking pins. A 2ms beat error is not great and shows that such a watch had a balance staff replaced without adjusting it afterwards. In some modern watches you can adjust both the rate and the beat error on the running watch. To adjust the beat error on a Hamilton 992b one has to take out the balance, carefully turn the balance collet and put it back. This is not easy. It requires a very steady hand and you might need to repeat this process a few times until you have the beat error below 1ms. A watchmaker might be tempted to take shortcuts thinking that and old watch will anyhow only sit in the drawer of a collector.

Top view of a typical 992B balance wheel with hairspring. The green dot marks the normal position of the hairspring stud (where it will be connected to the balance cock) and the red dot corresponds to the position of the impulse jewel (or roller jewel). The impulse jewel is normally not visible from the top since it is sitting on the other side. There is roughly a 90' angle between balance arm and the direction the impulse jewel is pointing to. Observe as well the distribution of the timing screws on the outer ring of the balance. It does not have to be exactly as in this drawing but my observation is that there is "one screw missing" in the direction towards which the impulse jewel is pointing (at 9 o'clock in the drawing). That pattern of screws is always mirrored to the other side of the balance ring.

To adjust the beat error you take the balance out and you remove it from the balance cock. I place it on a little wooden board that has a hole in the middle. This is to ensure that the balance is well supported. Make sure the board is clean and does not have any saw dust in the hole. The hole has to be just big enough for the roller table to fit in comfortably (about 3mm wide).

Top view of a typical 992B balance wheel with hairspring. The arrow points towards a slot in the hairspring collet. This balance has a few scratches on the balance arm just below the hairspring stud. Some watchmakers do that to mark positions. A more gentle method would be to use a sharpie permanent marker. Sharpie marks can be removed with alcohol. The other scratches might be from a balance staff replacement procedure that was a bit rough.
To adjust the beat error of the watch you put the smallest watchmaker screwdriver that you have into the slot on the hairspring collet and you turn it just a little bit. Be gentle and don't slip. You would ruin the hairspring if the screw driver slips. Turning it by an angle of maybe 2° makes all the difference between a beat error of 2ms and 1ms. So be careful. Put everything back together and check the beat error again with the timegrapher. If it increased then you have been turning in the wrong direction and you need to take it out again and turn in the other direction. There is no easy way to know up-front in which direction to turn since the needed change is so small and it is hard to see to which side it is off. You can stop when the beat error is below 1ms. A beat error of 2ms is not the end of the world either. Anything above 2ms should be corrected.

Timegrapher readings after beat error adjustment. This watch used to be at a beat error of 2.8ms. It took me 4 attempts to get it to 0.2ms.

Scribbling inside the case?

watch inspector repair markings on the inside of the case
Locomotive engineers, conductors, and switch yard controllers had to have their watches inspected and certified by the railroad's designated watch inspector. This was typically twice a year but some railroads required quarterly inspection. The inspector would check to see that the kind of watch was allowed by that particular railroad's rules and that it was in good running order (the requirement was typically +/- 30 seconds per week). Finding everything satisfactory, the inspector would certify the watch. Otherwise the watch would need to be repaired. The inspector was typically as well the watchmaker who would carry out those repairs. The railroad watch inspectors scribbled their number or some number letter combination into the back of the case if some sort of repair or cleaning was required. This way the inspector would easily know if they had worked on this watch before. They would as well keep paper records but these inspector repair marks where more convenient than searching through paper records.

In other words you know that a given watch was actually used on the railroad if it has those watch inspector repair marks on the inside back cover. These tiny scribbles proof that this is a real railroad watch.

watch inspection card

watch inspection certificate for a hamilton 992, 1974-Oct-05,

another watch inspection certificate
The Canadian National Railways followed the same principles as the railroad companies in the US. The watch inspectors filled out an "Employees watch rating card" which the employee had to carry with him while on duty. The the offset of the watch against standard time was recorded about every 30 days on the back of the card.

A CNR "Employees watch rating card" for a Hamilton 992B pocket watch

Hamilton 992B history

The Hamilton Pocket Watch Co started as the Adams & Perry Watch Manufacturing Co in 1874. It changed its name to the Hamilton Watch Co in 1892. The company had many failures until it became finally very successful. Click here for a full history and time line of Hamilton Watch.

The Hamilton watch factory around 1900

The Hamilton watch factory in 1912, employs about 750 people

The Hamilton 992B is a successor of the 992E (992 Elinvar, made from 1931-1941) which is a successor of the Hamilton 992 (made from 1903-1930). One of the main improvements in the 992B over the previous watches was the use of the "Elinvar Extra" hairsprings.

A Hamilton 992 from 1913, notice the cut bi-metallic compensation balance (the outer ring does not go all the way round, there is a cut)

The special alloy Elinvar, was invented in 1890. Elinvar is a special temperature compensated steel alloy (Fe 52%, Ni 36%, Cr 12%). The word "Elinvar" is an acronym made of the words "elasticity invariable". Because Elinvar does not expand as much with temperature as normal steel it simplifies the watch production process since it did not require the labor-intensive adjustments and did not need a bi-metallic balance to compensate the temperature coefficient of the hairspring . It is as well resistant to magnetism and does not easily rust. Hamilton had an interessting one page add in the Popular Science magazine issue in 1931 explaining Elinvar and advertising the Hamilton 992E pocket watch:

A Hamilton add for the 992 Elinvar in the Popular Science magazine, Nov 1931.

The Hamilton booklet: Elinvar in your watch, 1931, Click for the full PDF version.
source: nawcc.org.

This sounds fantastic but there were a few problems. Swiss watch companies used by 1930 already the Elinvar. Hamilton decided therefore to buy the Elinvar hairsprings from Swiss manufactures for its new 992E watches. The Swiss watches where however smaller and it seems they did therefore not see the same problems as Hamilton. Elinvar was softer than the steel hairsprings that it replaced. That meant that it was more easily damaged by watchmakers who worked on it during the frequent servicing that railroad watches had to endure. There were reports of the softer hairsprings sagging and coming in contact with the balance arms. Hamilton's watchmakers noticed that the railroad watches with Elinvar hairsprings did not run as strong as watches with steel hairsprings and bi-metallic compensation balances. The heat-treating process used in making the Elinvar hairsprings yielded a product that was unevenly striped in color and had to be dyed blue to look good.

Hamilton Industries, Elinvar Extra

Hamilton realized that it could not continue with the Swiss Elinvar and set out to develop a better hairspring alloy that would offer the the advantages of Elinvar without its disadvantages. They found the answer at International Nickel in the form of a product called Ni-Span-C. Hamilton obtained the rights to manufacture the alloy for use in hairsprings and it was first used in the new "B" series of watches that Hamilton introduced in 1940 (992B, 950B). Ni-Span-C has a constant modulus of elasticity at temperatures from -45°C to 65°C. The new alloy was called "Elinvar Extra" (Fe 48%, Ni 43%, Cr 5%, Ti 2.75%, Si 0.5%, Co 0.35%, Al 0.3%, C 0.04%). The name "Elinvar Extra" was probably chosen because Hamilton had invested so heavily in promoting the Swiss Elinvar that they wanted the word Elinvar in the new metal. This Elinvar Extra was indeed superior and the 992B (and other B-series watches) where the most accurate watches at the time.

The Hamilton 992B was introduced in November 1940 and produced until 1969 when the market had moved away from pocket watches to wrist watches. Wrist watches were able to achieve by 1969 similar accuracies as pocket watches. The other competition to the Hamilton 992B where pocket watches with standard Swiss Unitas movements made by small jewelers such as e.g the following Elco pocket watch from 1960.

Elco pocket watch with a Swiss Unitas 429 movement.
This watch was made (assembly of dial, case and movement) by Levy Brothers Co. Ltd. Hamilton, Ontario for the Canadian railroad. The Levy Brothers were Jewish immigrants from Alsace Lorraine who settled in the 19th century in Canada. They had a jewelery business. This watch is in functionality, appearance, size, weight and accuracy very similar to the 992B but it is more reliable in harsh working environments due to its Incabloc shock protection. I love the fact that both the Elco watch and the 992B are Hamilton watches. One made by a jeweler in the city of Hamilton, Canada and the other one from the Hamilton company. A little warning: if you ever service such a unitas 429 movement then watch out. This is probably the only movement were the screws on both winding gears are left threaded.

Here is the official announcement letter for the Hamilton 992B from November 1940:

Hamilton 992b announcement, 5 Nov. 1940
source: nawcc.org

A letter explaining the technical innovation that went into the Hamilton 992b was sent to selected jewelers, 6 Nov. 1940
source: nawcc.org

Page 28 and 29 from the 1940 Hamilton watch catalog.

The Hamilton 992b was sold for many years in a small velvet lined plastic box.

A Hamilton 992b from 1950 in its original velvet lined plastic box
with the original guarantee certificate.

The velvet lined plastic box was replaced in the 1960's by a cardboard box and the nicely decorated guarantee certificate was replaced by a little guarantee booklet.

A Hamilton 992b from 1969 with its original box and the original guarantee booklet.

Hamilton made about 525000 units of this magnificent pocket watch. All were made in Lancaster, Pennsylvania, USA.

Hamilton watch company plant in the 1940's, Lancaster, PA.

Hamilton watch company plant, 1945, Lancaster, PA.

You can still buy brand new Hamilton watches to this date. None of them are made anymore in the US.

Hamilton 992B serial numbers (find the age of your watch)

All 992B movement serial numbers start with the letter C. This serial number can be found on the movement (not the case).

C001-C13000....... 1940
C13001-C37900..... 1941
C37901-C62800..... 1942
C62801-C87700..... 1943
C87701-C112400 ... 1944
C112401-C137500... 1945
C137501-C175000... 1946
C175001-C199800... 1947
C199801-C254500... 1948
C254501-C281400... 1949
C281401-C310200... 1950
C310201-C352800... 1951
C352801-C385800... 1952
C385801-C408300... 1953
C408301-C415500... 1954
C415501-C423600... 1955
C423601-C441700... 1956
C441701-C448400... 1957
C448401-C455000... 1958
C455001-C461700... 1959
C461701-C468400... 1960
C468401-C475000... 1961
C475001-C481700... 1962
C481701-C488400... 1963
C488401-C495000... 1964
C495001-C501700... 1965
C501701-C508400... 1966
C508401-C515100... 1967
C515101-C521800... 1968
C521801-C525300... 1969

A few watches were assembled out of remaining parts in 1970 as part of a clean-up run and those serial numbers start with "4c1...."

Lever set (how to set the time on your railroad pocket watch)

A lot of pocket watches and all wrist watches are pendant set. The 992b is not.

On a pendant set watch you would pull the crown and then change the time. The crown is as well used to wind the watch. This is a problem if you try to wind your watch and you are on a moving train. The train track is possibly not very even and you might end up changing the time while you wind your watch. You could as well pull the crown while you push the watch into your pocket.

Lever set was invented to prevent the accidental setting of time while winding the watch. To set the time you unscrew the crystal and you pull a small lever (with your finger nail) in the upper right corner near 1 o'clock. Now you can turn the crown and set the time. You can set the hour and minutes hands (you can't change the small seconds hand). American railroad watches are very accurate and do not need to be set every day.

Push the lever back in when done, and re-attach the crystal.

Hamilton 992B maintenance and repair

Your Hamilton 992B might already be older than you and it will outlive you if you take good care of it. It is a high quality mechanical device but it wants to be treated gently and requires good care. It's not shock proof (don't hit it or drop it) and it is not even water resistant. Mechanical watches require cleaning and oiling about every 5 years.

The US army used the Hamilton 992B during the second world war and there is a maintenance manual from the "War Department" called "TM 9-1575" which can be very helpful when servicing a 992b:

The full TM 9-1575 as pdf, black and white, 14937992 bytes
Just the pages about the Hamilton 992b, pages 84 to 103, tan color, 6688589 bytes

Note that the pocket watches used by the army had a tire like rubber around the watches to protect them. The manual talks therefore about removing that rubber shock absorber.

Proper service and oiling is very important for a mechanical watch. Modern synthetic oils require less frequent service but it is still required. A watch that is erratic (sometimes a little too fast sometimes a little too slow) requires service. A properly oiled watch looks dry at first glance. There are just tiny amounts of synthetic oil needed:

proper and improper oiling (TM 9-1575)

A watch that is missing oil runs at low amplitude (runs weak). You can actually see it by looking at the running balance. My experience is that a lot of watches sold via ebay suffer from a low amplitude problem. It seems that most semi professional watch dealers just clean the watches and make them shine. They don't bother to oil them properly. A watch running at low amplitude will never keep time over a longer period.

Cleaning and oiling caped jewels

Caped jewels are used for all bearings with fast rotating or oscillating wheels where proper lubrication (not too much and not too little) is very important. Old watches that might not have been serviced for 40 years could have a film of tar like old dry oil on those caped jewel stones. Take a toothpick (a normal wooden toothpick, not one made from bamboo, bamboo is too hard) and sharpen it with a knife. Sharpen it such that it has a very fine long tip. Put a drop of oil onto the tip of the toothpick and push it gently into the jewel hole. Turn the toothpick to clean the jewel.

Take a piece of paper, cut off a triangular shape and then use the tip of the triangle to remove the oil from the jewels. The paper will absorb the oil and take some of the diluted old oil with it.

Finally oil the jewel with one drop of high quality watch oil. Push that oil into the space between the jewels with a thin copper wire as shown in the picture on the right. Note that some those jewel holes are very very small. You need one single strand from a very fine stranded copper wire.

Watch parts that must not be oiled

There are a few parts that must not be oiled at all otherwise the watch will not work properly:

Cannon pinion: The cannon pinion is attached with a friction fit. The friction between the axis and the cannon pinion allows you to set the time. If you oil it then hour hand and minute hand will behave erratic despite the watch running at a constant frequency.
Pallet fork, the side towards the roller jewel (the stone on the balance wheel). If you oil it then the roller jewel will stick for a moment to the oil while it is trying to get away from the fork. The balance wheel will loose energy and the watch will not run as strong as it could.
Hair spring. The hair spring must be totally dry otherwise the timing will be completely off. An oily hairspring will cause the watch to run too fast and too fast in an erratic way.

How to apply oil to a watch

A hollow needle oiler will not work for a pocket watch. It will cause you to apply too much oil and just create a mess. What you need is a "dip style" watch oiler. You can easily build one yourself. You need a gauge 24 (0.5mm diameter, 0.2mm²) steel or brass wire. Tap on the end of the wire with a hammer such that it becomes flat and then dull any sharp edges with fine sand paper (it should be a round tip, like the shape of a drop). A wooden dowel or a piece of a twig cut from a tree can serve as a handle.

A self made dip style watch oiler. First photo: the parts you need. Second photo: the tip of the oiler. Third photo: the final oiler pen.

The dip oiler is used as follows: You dip the tip (not the whole wire) into suitable synthetic watch oil. A tiny amount of oil will stick to the end of the oiler and then you can use it to precisely apply a tiny drop by touching the spot where you want to have oil with this oiler pen. This is the best way to oil a pocket watch.

For some applications you will need a really small dip oiler and here is how to build one.

A very small self made dip style watch oiler. First photo: we use a single brass wire from a brass brush as used for cleaning a barbecue. Pull it out with pliers and make the ends a bit flat by banging on it with a light hammer. Second photo: get a syringe needle from the pharmacy, dull it with sand paper and insert the brass wire into it. Squeeze the needle with pliers to hold the wire. Third photo: magnified view of the tip of this oiler pen, make the ends smooth by running it over an oil stone.

Keeping dust out of the movement

Dust particles, especially larger ones, can be a big problem for a mechanical movement. They can sit on-top of the hairspring and change the timing completely or they can cause trouble to the escape wheel and other fast moving parts. You should therefore avoid to open the movement too frequently. Look out for any lint that has accumulated around the back cover after carefully opening it. Remove the lint with a clean cloth.

I put a drop of oil inside the back cover and distribute it with my finger evenly. This will cause any remaining dust particles in the movement to stick to the cover. It's like a dust magnet that removes over time all remaining dust particles from the inside of the movement.

How to carry a pocket watch

Vintage pocket watches are not shock proof. They loose their capability to keep time or they break completely if you drop them on the floor. It is therefore very important to attach them to your vest or pants with a chain. This will prevent the watch from falling down in case it slips accidently out of your hands.

The problem is that a metal chain causes scratches on the case. The "brassing" (worn out gold case) that you see on some watches is due to the watch rubbing on the chain while beeing carried in the pocket. Chains cause small scratches on watch crystals especially on plastic crystals.

I like to use my watches and not just keep them in a drawer. Thin and round (not flat) 30inch (76cm) shoe laces make perfect watch chains. Shoe laces are good strings. You can easily tie a knot that holds yet the string stays straight and does not get all messed up while you have it in your pocket. Shoe laces are soft and don't damage the watch case.

Thin shoe laces as a watch chain. They are stong and don't damage the watch.You can tie two knows as shown and attach them to a belt loop on your pants or a button hole on your vest.

Hamilton Railroad

Vintage Hamilton advertisements, pocket watch adds

Most of the larger pocket watch adds from Hamilton are for watches that pre-dated the 992B. The adds for the general public posted from the 1940's and 1950's (when 992B was in production) were for wrist watches. Hamilton did however post 992B pocket watch adds in specific railroad magazines.

Adds posted in the ERIE railroad magazine:

The adds below are all pre 1940 adds for the Hamilton 992 (without the B) or other models from that time. The Hamilton 992 is the most successful of all Hamilton pocket watch movements. The 992B pocket watch movment is an improved version of the 992 but it did not sell as much because in the 1940's, when the 992B came to the market, the trend was already going towards wrist watches.