Marco Mainspring #1261 for New England Series ZZ "Cavour" movements - Steel

Marco Mainspring No.1261 for New England Series ZZ "Cavour" movements, Factory #46, steel, new in envelope. See images for precise mainspring specification. This absolutely precisely fits a Series ZZ, but it will fit a Series Z and a perhaps a Series O as well, it's just a tiny bit longer than the stock mainspring was. 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.