Illinois Factory Mainspring Factory No. 47377 for 12/0s movements - Steel

Illinois Factory Mainspring for 12/0s wrist watch movements, Factory No. 47377, steel, new in frail envelope. One of the beautiful thing about factory mainsprings is that they pretty much always fit. See images for further details. I specialize in hard to find watch parts and all watch parts are unconditionally guaranteed. Images do a pretty good job of representing the item.