Repairing a World War II Navy Chronometer - The Iconic Hamilton Model 21

#restoration #watchrepair #clock
This is the most expensive broken watch (or clock?) I've purchased on eBay. It was sold to me at a "discounted" price of about $1,600 due to issues that I'll uncover and repair in this video. It's hard to call this a "deal" at that price, but in the end it was worth it.

World War II created a dire chronometer shortage for the United States. Before the war, most chronometers for American military and civilian customers were imported from Europe so we had that unfortunate supply chain dependency on that part of the world. In 1939, anticipating war, the U.S. Naval Observatory sought American watch manufacturers to mass-produce chronometers. Hamilton and Elgin participated, but only Hamilton met the Navy’s accuracy standards. Early 1942, Hamilton’s prototypes were selected after passing with a +/-1.55-second daily error rate. During the war, Hamilton produced approx 8,900 chronometers for the Navy, 1,500 for merchant ships, and 500 for the Army. In contrast to other movements of the time, Hamilton incorporated the detent escapement and the helical, corrosion resistant elinvar balance spring to maximize the accuracy it could produce.

These chronometers were specialized timekeepers for determining longitude at sea. A chronometer set to a known time standard like Greenwich mean time, allows sailors to determine their longitude by comparing it to local time. Since one hour of time difference equals 15 degrees of longitude, the time gap between the chronometer and local time reveals the ship’s longitude.