Felsa 4000

Swiss automatic movement introduced around 1955-1960 with several innovative features. Built on the manual-wind Felsa 4010 base with a piggybacked self-winding module. First Felsa to use a rocking bar changer for bidirectional winding. Features nickel screw balance with swan neck regulator. Available in elaborate versions with up to 35 jewels using KIF-Duofix bearings throughout. Widely rebadged including as Elgin 813. Related calibers include 4005, 4007 (with date), and 4010 (manual base).