Hamilton Factory 16s Mainspring Factory No. 317 or 318 - Steel

Hamilton Factory Mainspring for 16s 17 Jewel Movements (such as the 974), Factory No. 317 or 318, steel, new in likely very frail envelope. See image for precise characteristics. I call this the "use this mainspring if you don't know which one you need" mainspring as it's generic enough for just about any non-RR Hamilton grade, of which there were many. 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 an adequate good job of representing the item.