NuRezista Mainspring #643 for Hamilton 6/0s No. 2521- Steel

NuRezista Mainspring #643 for Hamilton 6/0s movements, Factory No. 2521, steel, new in dirty envelope. See images for further details and precise mainspring specifications. 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 unconditionally guaranteed. Images do an adequate job of representing the item.