Marco Mainspring #701 for N.Y. Standard 18s No. 2189 - Steel

Marco Mainspring #701 for N.Y. Standard 18s Movements, Factory No. 2189, hole end, steel, new in frail or torn envelope. See images for further details. I likely have several of these so the one you get may differ slightly from the images. Note that the really super old Marco number for this was 4180 and the equally super old factory number for this was 1529.  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.