The need for Railroad Watches to be "railroad approved" stemmed from a number of train accidents in the late 1800's where two trains collided head on due to poor time keeping.
Regular watch inspection and consistent time keeping was the only thing that kept trains from running into each other on Americas single track railways. His first job as a time inspector was when he was brought in by the Lake Shore and Michigan Southern Railways in 1891 after a crash and was tasked with bringing their time inspection system up to industry standards.
Credit is usually given to Hamilton's Chief Physicist at the time, John Van Horn, and his teammates, physicist Phillip Biemiller and Master Technician James H. The Model 500 movement made use of a battery that was co-developed by Hamilton, and the National Carbon Company (which later became Union Carbide) which agreed to work with them after over 40 other battery makers turned them down.
The battery was designed to be leakproof and provide very constant voltage.
Though Hamilton was the very first to offer a battery powered watch to consumers, it was a victory that came at a significant cost, in the end.
The first electric clocks go back quite a long way; in 1814, Sir Francis Ronalds invented the very first (which is pretty amazing when you consider that Breguet had patented the tourbillon only thirteen years earlier).
If you are sufficiently active while wearing the watch throughout the day (for at least an 8-hour period), the watch should maintain a power reserve for between 24-36 hours. Turn the crown forward (clockwise) with a long stroke.
Turn the crown clockwise until it stops abruptly and cannot be wound any further.
A manual-wind timepiece should be wound until resistance is felt and the crown will no longer turn clockwise, whereas an automatic watch can be found forever without risk of damage.
Many other countries solved the root cause of the problem with station to station communication, signaling, tokens or dual track.
In this article we focus however on watches and it is this focus on timing only that lead to those beautiful and precise American railroad watches.