Marco Mainspring #731 for NY Standard 12s Excelsior No. 1322 - Steel

Marco Mainspring No. 731 for NY Standard 12s Excelsior model movements, Factory No. 1322, steel, 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 in hard to find watch parts and all watch parts are unconditionally guaranteed. Images do a pretty good job of representing the item.