Progress Mainspring for 12s Illinois Factory No. 47345 - Steel

Progress Mainspring for Illinois 12s movements, Factory No. 47345 (old # 1236), steel, new in envelope. See images for further details. Dennison 11 x 4 x 19½ and is not an easy number to find. I likely have several of these so the one you get may differ slightly from the images. 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.