Railroad grade pocket watches were built to conform to the General Railroad Timepiece Standards specifications, a set of technical requirements designed to ensure that train engineers and other rail company employees would carry timepieces that were accurate, reliable, and durable. The mass production of these precision pocket watches, many with interchangeable parts, movements, cases, and dials, was an amazing feat of industrial engineering at the time, and has left us with a legacy of wonderful pocket watches that keep very good time today. Here collectors can find all the great old American pocketwatches from Waltham, Elgin, Howard, Hamilton, Illinois and others, with a new collection of historic timepieces appearing daily.
Some sources of information on the history of railroad grade pocket watches and other topics of interest to watch and clock collectors and horology enthusiasts.
The place to start is Horology - The Index, the website of the National Association of Watch and Clock Collectors, or NAWCC. There you can find horological organizations, information on horological science and the development of timekeeping devices, and useful tips on antique pocket watch repair and restoration as well as buying, selling, appraisal and collecting antique watches and clocks. They also have a very nice virtual watch and clock museum tour with all kinds of interesting horological information and pictures.
To get a quick overview of the development of portable timepieces, from clock-watches of the 16th century to the railroad grade pocket watches of the late 19th century, see wiki's watch page.
To find definitions of words used for the various parts of watch movements and other technical terms used in horology, see Barry Goldberg's watch information page.
If you would like to understand the intricacies of how things like balance wheels and lever escapements work, check out The Horologium.
Some interesting perspectives from noted collectors of antique pocket watches:
Vintage watch and clock expert Jonathan Snellenburg talks about the societal forces driving watch and clock technology and the historic cultural changes that resulted from better timepieces, as well as technical details of the progression from the verge escapement through pocket watches to wrist watches.