Swartchild Black Shield Mainspring #440511 for Elgin 4/0s No. 4789 - Steel

Swartchild Black Shield Mainspring #440511 for Elgin 4/0s, Often called the Legionaire series, Factory No. 4789, steel, new in envelope. See images for further details. This particular one is covered in grease not unlike Elgin factory mainsprings (because it probably is one) and will need to be cleaned thoroughly before use. 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.