Hampden Factory Mainspring 12s No. Factory No. 12696 - Steel

Hampden Factory Mainspring for 12s movements, Factory No. 12696, steel, new in frail or replacement envelope. See image for further details. I likely have several of these so the one you get may differ slightly from the images.  I specialize is hard to find watch parts and all watch parts are guaranteed. Images do a pretty good job of representing the item