Illinois Factory Mainspring No. 47321 for 16s movements - Steel

Illinois Factory Mainspring, Factory No. 47321 for 16s movements, steel, new in frail  envelope. See images for further details. One of the beautiful thing about factory mainsprings is that they always fit. 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.