Hamilton Factory Mainspring for 16s 17-21j Factory No. 718042 (317) - Steel

Hamilton Factory Mainspring for 16s 17 - 21 Jewel Movements (such as the 956, 964, 965, 968, 969, 974 thru 987), Factory No. 718042 / 317, steel, new in 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 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.