NuREZISTA Mainspring #539 for 20/0s Elgin Factory No. 5015 - Steel

NuREZISTA Mainspring #539 for 20/0s Elgin Movements, Factory No. 5015, steel, D.B. end, new in envelope. See image for precise characteristics. 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 guaranteed. Images do a satisfactory job of representing the item.