Marco Mainspring #580 for 6/0s Illinois Factory No. 47364 - Steel

Marco (C&E Marshall) Mainspring #580 for 6/0s Illinois Open Face 1st and 3rd models, Factory No. 47364 (old #1422), 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.