Newall Security Mainspring #662 for Hampden 8/0s Factory No. 15696 - Steel

Newall Security Mainspring #662 for Hampden 8/0s "Mary Jane" & "Josephine" movements and likely others as well, Factory No. 15696, steel, new in envelope. Swartchild Mainspring Catalog (which I sell) lists this as a Dennison 3.5 x 8. Have several so the one you get may have a slightly different envelope. See image for further details. 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.