BESTFIT Mainspring JA508 for N.Y. Standard 12s Factory No. 4284 - Alloy

BESTFIT Mainspring MS-JA508 for N.Y. Standard 12s Movements, Factory No. 4284, Tongue End, alloy, new in envelope. See images for further details. I likely have several of these so the one you get may differ sightly 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.