Elgin DuraPower Mainspring for 13/0s grade 730 & similar - Alloy

Elgin DuraPower Mainspring for 13/0s grade 730 which is a 21j B.W. Raymond movement, alloy, new in envelope. Often not an easy mainspring to find. I likely have several of these so the one you get may differ slightly from the image. I specialize is hard to find watch parts and all watch parts are guaranteed. Images do a very good job of representing the item