Swartchild Black Shield Mainspring #4365 for Elgin 0s No. 825 - Steel

Swartchild Black Shield Mainspring #4365 for Elgin 0s, Factory No. 825, 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 is hard to find watch parts and all watch parts are unconditionally guaranteed. Images do a pretty good job of representing the item.