NuREZISTA Mainspring #743 for South Bend 12s No. 55528 - Steel

NuREZISTA Mainspring No. 743 for South Bend 12s, Factory No. 55528, steel, new in envelope. See images for precise mainspring specifications. 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.