Possibly from the AS 1121 ebauche, not a lot of info available. Not listed in Bestfit. 17j, Breguet overcoil. An example here:
Image courtesy of: Timerestoration
Another Movement uncovered in a recent Watchmaker's Estate purchase. I can find no record of this caliber. Also, not sure about sequence of serial number on these early models...this one is 1349...very close to the 1310 of the 21 Jewel Phantom movement I previously listed, which another member dates to 1926.