USR Mainspring for Illinois 0s No. 47359 - Steel

USR Mainspring for Illinois 0s movements, Factory No. 47359 (really old No. 981), steel, new in frail envelope. See images for further details. 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.