Cas-Ker Mainspring JA743 for 12s Waltham Colonial B Factory No. 2237 / 2267 - Alloy

Cas-Ker Mainspring MS-JA743 for 12s Waltham Colorial B movements, Factory No. 2237 /  2267, almost certainly made by Bestfit, new in sealed package. See images for further details. I likely have several of these so the one you get may differ slightly from the images. I specialize in hard to find watch parts and all watch parts are unconditionally guaranteed. Images do a pretty good job of representing the item.