Before standard time, a railway ran on the time of its own headquarters, and a conductor's watch was a private instrument. The adoption of standard time in North America in 1883 turned timekeeping into an operational safety system, because trains on single-track routes were separated by schedule rather than by sight.
Individual railroads, not a single national body, wrote the resulting rules. Requirements converged on a recognisable pattern — a minimum jewel count, adjustment to temperature, isochronism and several positions, lever setting to prevent accidental hand movement, an open-face case with the winding crown at twelve, a plain Arabic dial with bold minute markings, and periodic inspection with recorded rate.
The frequently repeated story that the 1891 Kipton collision alone produced these rules compresses a longer process. Inspection systems were already developing, and standards continued to tighten into the twentieth century. Treat the single-event version as tradition rather than documented cause.
For manufacturers the specification was transformative. It created a guaranteed high-grade market with published criteria, which rewarded factories capable of consistent adjustment work: Hamilton, Illinois, Elgin, Waltham and others all built flagship grades around it.
Identification follows from the specification. A railroad-grade watch is recognised by its configuration — jewel count, adjustment markings, lever setting, dial layout and case type — rather than by the word 'railroad' on a dial, which appears on many watches that never met any standard.
Research a candidate in this order: read the movement grade and serial, look it up in published factory tables, confirm the adjustment markings, check whether dial and hands are of the correct type, and only then consider whether the case is original to the movement. Inspection records, where they survive in collections, are the strongest documentary evidence a railroad watch can carry.