Hamilton Factory Mainspring for 16s 17-21j Factory No. 718041 (317) - Steel

Hamilton Factory Mainspring for 16s 17 - 21 Jewel Movements (such as the 974 & 992), Factory No. 718041 / 317, steel, new in possibly frail envelope. See images 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 so I usually have whatever you might need and all watch parts are unconditionally guaranteed. Images do a pretty good job of representing the item.