Swartchid Black Shield Mainspring #4358 for 16s Elgin Pocket Watch No. 817 - Steel

Swartchild Black Shield Mainspring #4358 for 16s Elgin Pocket Watches, Factory No. 817, steel, new in envelope. See images for precise mainspring specifications. Pretty sure these ones were made by Elgin. 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.