Marco Mainspring 2810M for Gruen caliber 720 & 721 Pocket Watch movements - Alloy

Marco Marshalloy Mainspring 2810M for Gruen caliber 720 & 721 plus UT 429 pocket watch movements and perhaps others, new in envelope. See images for precise mainspring specifications. 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.