HR Mainspring A311 for 12s Hampden Factory No. 12696 - Steel

HR Mainspring A311 for Hampden 12s movements, Factory No. 12696, T End, steel, new in well-handed envelope. I believe this mainspring is made primarily for the Paul Revere and Nathan Hale models. See images for precise specifications. I likely have several of these so the one youget 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.