Hamilton Factory Mainspring for 20/0s & 21/0 Hamilton Factory No. 2921 - Steel

Hamilton Factory Mainspring for 20/0s & 21/0 Movements, Factory No. 2921, steel, new in envelope. See images for precise characteristics. These were available in a couple of different strengths and those that I can supply can be found in the drop-down list. I likely have several of these so the one you get may vary 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.