The Gruen 156D watch movement is an automatic movement with two roller freewheels and a jewel-bearing rotor. It is based on the modified Peseux 336 base movement, with the automatic module added on top. The movement features a jewel-bearing for the barrel and includes functions such as automatic winding, sweep second, and date adjustment within a range of +/- 24 hours. The Gruen 156D movement was first used in watches starting from 1957.