This is the inside of a vintage Omega Electronic F 300 Hz wristwatch. Although this tuning fork movement was designated by Omega as a caliber 1260, the base movement is an ESA 9164 found in several other watches from Baume et Mercier, Eterna, Longines, Tissot, etc. This particular watch was experiencing the dreaded spinning second hand issue when adjusting the time (you can watch a video of it here, and learn more about why that happens here). Enjoy the gut shot photo gallery below!