Elgin Railroad Watch
Before the advent of the train travel, timepieces were luxury items for those who could afford them. Train schedules made having a watch important for a larger segment of the population.
Following a train crash in 1891, it became necessary to have rules for the watches used by railroad staff. This led to the General Railroad Timepiece Standards, which mandated standards for railroad watches:
" .... 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 per 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..."
[Timezone]
Here is a 16-size Elgin pocket watch with 21 jewels, made to railroad specifications in 1930. The hands are set by pulling out a lever (see first photo) and turning the crown. The gears, the jewel settings and the balance screws are gold. The pallet fork is poised. Most importantly, the hairspring is white alloy metal, not blue steel. The white Elinvar alloy, made of nickel and steel, is virtually unaffected by changes in temperature, so there is no requirement for temperature compensation. Watches with white hairsprings are considerably more accurate.
Link:
[Wikipedia]
