HR Mainspring SA729 for Waltham 0s Factory No. 2220 - Alloy

HR Mainspring SA729 for 0s Waltham, Factory No. 2220, alloy, new in likely dirty envelope. See image for precise mainspring specifications. 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 an adequate job of representing the item.