Hamilton Factory Dynavar Mainspring for 10s #717101 - Alloy

Hamilton Dynavar Factory Mainspring for 10s Movements, more specifically the 917, 921, 923 & 945 models, Factory No. 717101, alloy, new in envelope. See images for further details. 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 good job of representing the item.