Hamilton Factory Mainspring for 18/0s Hamilton No. 2721 - Steel

Hamilton Factory Mainspring for 18/0s Hamilton 17j Movements, Factory No. 2721, steel, new in envelope. See image for precise characteristics. 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.