The Hamilton Watch Company was founded in 1892 with one purpose - to make the finest time pieces available in America in order to keep American railroads safe. Railroads criss-crossed the country and typically trains moved both directions on the same line. It was critical that trains kept to a strict time schedule in order to prevent two trains traveling opposite directions from colliding.
The accuracy required to keep railroads safe across the country was a daunting challenge. A time standard had to be defined and everything aligned to it with a level of accuracy in terms of seconds per week!
Hamilton rose to meet that challenge and by the 1920s thousands of high quality pocket watches were produced each year. It's one thing to create a single movement with such exceptional time keeping. It's another thing to make thousands of watches, each with the same level of quality. It was said that you could take 100 Hamilton movements, completely disassemble them, mix all the parts together, and reassemble 100 working movements. That's saying something.
"Railroad grade" really depended on the railroad in question. The requirements differed across railroads. You had local transit systems and cross-country rail networks with no single definition. Eventually a common standard evolved and it included several attributes such as... it needed to be 16 size or larger, it needed to be open-faced with the pendant at 12, it needed a minimum of 21 jewels (sometimes less but not less than 17), it needed to be certified accurate to within 30 seconds per week, etc. etc.
For the most part, the entry-level Railroad Grade watch for Hamilton was the 992, at least in 16 size. The 940 was the most common 18 size movement. The 992 was produced for decades starting in the early 1900s, with enhancements made over the years.
Back in the day, if you wanted to purchase a watch you would go to your local jewelry store. Jewelers would carry an inventory of movements from different makers along with cases made by various case makers. The customer could choose their movement and then their case and the jeweler would fit the two together for sale. You could purchase a top of the line movement and put it in a base metal case or a 7 jewel movement and case it in solid 18K gold. It was entirely up to the buyer - although railroad models had to meet certain requirements.
Typically, for older models you'll find cases with "warranties" for wearing through the gold layer based on years... so a 10 year warranty would have less gold than a 15 year warranty, which would have less gold than a 25 year warranty. When the case is marked "permanent", then it's solid gold. Eventually the jewelry standards for "gold filled" were established and the industry adopted the standard for pocket watches in cases marked 10K gold filled, 14K gold filled, or solid gold, and so on, including stainless steel.
Personally I think all pocket watches have a cool factor. Although the utility of them is fairly limited today. A lot of collectors focus on railroad-approved examples and you could spend a lot of time and money developing a well-curated collection of the various Hamilton examples. However, Hamilton made beautiful dress pocket watches too. So the sky is the limit if you really caught the pocket watch bug.
My project watch is actually a part of my personal collection. I've had it for many years and I rarely use it. However, the oil inside any mechanical watch eventually evaporates so even watches that have little to no use need to be serviced every few years if they're to be kept in running order. I'm not sure how long I've had this example and I don't see my service mark inside so this may predate my ability to service watches.
The case is 10K gold filled and was made by Keystone, another Pennsylvania company, like Hamilton. The bezel is knurled so it's easier to unscrew to get to the set lever (another railroad requirement). The dial is "double sunk" with three surfaces... one for the hours, the center, and another for the seconds register. The dial is enamel and often presents with a chip or crack somewhere. This dial is excellent.
