Definition
A watch key is a small tool used to wind up and set the time on older mechanical watches. It's a small key that fits into a specific hole on the watch case. Think of it as the ignition key for your grandfather's time machine. Watch keys are usually made of metal and come in different sizes to fit different watches. Modern watches are usually automatic or battery-powered, making watch keys mostly obsolete. It's a relic of a bygone era of watchmaking.