The 1893 General Railroad Timepiece Standards.
While there had been discussions of timekeeping standards as early as 1853, when the Superintendent of the Boston and Providence Railroad instituted the first watch inspection program to determine whether the watches used were "fit to be trusted or not," It is the 1893 General Railroad Timepiece Standards that first defined and identified a true Railroad pocket watch. Watches used for railroad timekeeping were required to meet the following specifications:
“Be open faced, size 18 or 16, have a minimum of 17 jewels, adjusted to at least 5 positions, keep time accurately to within a gain or loss of only 30 seconds a week, adjusted to temperatures of 34 to 100 degrees Fahrenheit, have a double roller, steel escape wheel, lever set, micrometric regulator, winding stem at 12 o’clock, grade on back plate, use plain Arabic numbers printed bold and black on a white dial, and have bold black hands.”
Webb C. Ball was instrumental is establishing the "Time Service," the system of watch inspections, and any watch that gained or lost 30 seconds or more in 7-14 days had to be repaired by an experienced and approved watch inspector. Because this system was widely adopted and strictly adhered to, American watch manufacturers were forced to develop and produce a superior railroad watch, thus assuring increased safety for the traveling public.
The railroads never reached complete agreement on a single standard, but the key point is that as technology evolved, so did performance requirements for railroad watches. Some of the larger railroads had their own requirements and established their own system to administer the rules. For example, some required a Breguet hairspring and adjustment for isochronism and temperature. Dark blue hands were also acceptable in most cases.