Marco Mainspring #520 for 16s Illinois Bunn & Sangamo Special Factory No. 47330 - Steel

Marco Mainspring #520 for 16s Illinois Bunn & Sangamo Special Factory No. 47330, steel, new in envelope. See images for further details. Pretty darn sure these are just repackaged factory mainsprings. 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.