Elgin Factory DuraPower Mainspring for 13/0s 24hr Military Hack Grade 729 - Alloy

Elgin DuraPower Factory Mainspring for 13/0s Grade 729 24hr Military Hack Watches from the early 1960's, Refill #258 - 729, alloy, new in package. Do not come across these very often, see images for further details. I likely have several of these so the one you get may differ very 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.