Gruen 763

The Gruen 763 is a manual winding movement manufactured in the United States from 1934 to 1942, with approximately 531,500 units produced. It features a bimetallic screw balance, Breguet hairspring, and a safety barrel design incorporating a ratchet wheel and joint spring core to reduce bearing pressure and prevent damage from a broken spring. The movement was produced in three grades offering 9, 15, or 17 jewels. Production ceased in 1942.