Swartchild Black Shield Mainspring #440171 for Waltham 12s Factory No. 2237 - Steel

Swartchild Black Shield Mainspring #440171 for 12s Waltham Factory No. 2237, steel, new in envelope. See images for precise mainspring specifications. 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.