Progress Mainspring for 16s N.Y. Standard Factory No. 1321 - Steel

Progress Mainspring for N.Y. Standard 16s movements, Factory No. 1321, 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 suitable job of representing the item.