Hamilton Factory Dynavar Mainspring for 21/0s Hamilton No. 717572 - Alloy

Hamilton Factory Dynavar Mainspring for 21/0s Movements, Factory No. 717572, alloy, new in envelope. Made for many grades of 21/0s Hamilton's but mostly those in the 700 grade range (756, 757, 761, 780). See image for further information characteristics. I likely have several of these so the one you get may differ slightly from the images with some in factory envelopes and some not. I specialize is hard to find watch parts and all watch parts are unconditionally guaranteed. Images do a pretty good job of representing the item.