Information about Fusee Watches

The fusee watch was said to have been invented by Leonardo da Vinci, and it was an early attempt to regulate the power in the mainspring, so that the watch could run at the same speed as the spring winds down.

A mainspring tends to give less power as it winds down, so the fusee equalizes the power by changing the gearing. A chain is used to drive different gears as the spring winds down. Thus, the tension is equalized as the spring unwinds.

Better methods were developed using a hairspring and balance wheel, beginning around 1850 for most American pocket watches. Please note that most fusee watches wind through the back with a key in the counter (anti) clockwise direction. Do not force the winding shaft in the wrong direction or damage to the watch might occur.