Swartchild Black Shield Mainspring for Illinois 16s Motor Barrel No. 47331 - Steel

Swartchild & Co Black Shield Mainspring No.440901 for Illinois Motor Barrel, Factory No. 1952 or 47331 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.