Swartchild Black Shield Mainspring 440641 for 12s Hampden No. 12696 - Steel

Swartchild Black Shield Mainspring No. 440641 for Hampden 12s Paul Revere Movements, Factory No. 12696, T end, steel, new in envelope. See images for further details. 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.