3H Monogram Mainspring for N.Y. Standard 3/0s No. 2041 / 1323 - Steel

3H Monogram Co. Mainspring for 3/0s New York Standard, Factory No's 2041 / 1323, steel, new in envelope. Not an easy mainspring to find and I'd never seen this maker before acquiring a few earlier this year. I specialize is hard to find watch parts so I usually have whatever you might need and all watch parts are unconditionally guaranteed. Images do a pretty good job of representing the item.