Swartchild Black Shield Mainspring #4358A for Elgin 16s No. 2542 - Steel

Swartchild Black Shield Mainspring #4358A for Elgin 16s, Factory No. 2542, steel, new in envelope. See images for further details. 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.