So like the title says, the main spring broke on this watch. I'm repairing and I've looked all over it. I can't find a caliber number not on the main body not under the balance wheel. Nowhere I can only find this apparent serial number on the dial side of the main body. I'm hoping somebody can see the gear, train or general layout of the movement and help me identify the proper mainspring because I really don't want to have to try and measure it…

Broken mainspring on my a schild Swiss movement and I need help finding the caliber for replacement