USR Mainspring for Elgin 5/0s No. 2705 - Steel

USR Mainspring for Elgin 5/0s Movements, Factory No. 2705, new in frail envelope. USR is short for Ulysse Sandoz-Robert of La Chaux-de-Fonds, Switzerland. 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 pretty good job of representing the item.