The Alpina 668 watch movement, produced between 1910 and 1923, is an open face calibre featuring a monometallic screw balance with a press-fit staff. It utilizes a Breguet hairspring and offers optional separate crown-wheel bridge. Variations in design exist between early and later samples, including differences in the lever bridge, brass lever, and escape wheel in early models, while later models feature a lever cock, steel lever, and escape wheel. Detailed modifications can be noted throughout the production period in reference to available photographs. The balance with press-fit staff and riveted staff are fully interchangeable with the hairspring. The J9 movement offers stem winding and setting functionality, as well as a sub-second feature.