NuREZISTA Mainspring #652 for 21/0s Hamilton No. 2921 - Steel

NuREZISTA Mainspring #652 for 20/0s & 21/0s Hamilton Movements, Factory No. 2921, steel, T end, new in very distressed envelope. See image for precise characteristics. I specialize in hard to find watch parts and all watch parts are guaranteed. Images do a pretty good job of representing the item.