Marco Mainspring #458 for Hamilton 10s No. 6021 - Steel

Marco Mainspring #458 for Hamilton 10s Movements, Models 917 & 921, Factory No. 6021, steel, new in envelope. See image for specifications and further details. Regardless of the misinformation on some of the the envelopes this is for the 917 thru 921 not a 971 and these are really 10s movements. 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 and all watch parts are unconditionally guaranteed. Images do a pretty good job of representing the item.