USR Mainspring for South Bend 6s No. 3528 - Steel

USR Mainspring for South Bend 6s Movements, Factory No. 3528, steel, new in very frail envelope. See images for further details. I likely have several of these s the one you get may differ slightly from the images. I specialize is hard to find watch parts and all watch parts are unconditionally guaranteed. Images do an adequate job of representing the item.