I have an ETA 2750 movement and I need to replace the mainspring. My catalogs don't cover this caliber. The current mainspring, based on my measurements has the dimensions Dennison (Metric), W: 5 1/2 (1.45 mm), T: 9 (0.13 mm), L: ~ 14 1/2" (368 mm). However, due to its age and the fact that it's...