Marco Mainspring #531 for 12s Illinois Factory No. 47350 - Steel

Marco Mainspring #531 for 12s Illinois Motor Barrel models, Factory No. 47350, steel, new in possibly frail envelope. I likely have several of these so the one you get may differ from the images. I specialize is hard to find watch parts and all watch parts are unconditionally guaranteed. See image for precise characteristics. Images do a pretty good job of representing the item.