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 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.