Swartchild Black Shield Mainspring #4378 for Illinois 14s & 16s No. 47334 - Steel

Swartchild & Co Black Shield Mainspring No.4378 for Illinois 14s & 16s, Factory No. 365 or 47334 depending on your reference, steel, new in envelope. 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. mages do a pretty good job of representing the item.