Hamilton Factory Mainspring for 10s Hamilton No. 718101 / 6021 - Steel

Hamilton Factory Mainspring for 10s Movements, No. 718101 / 6021, steel, new in envelope. See images 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 marginally adequate job of representing the item.