NuREZISTA Mainspring #718 for Hampden 16s Factory No. 3696 - Steel

NuREZISTA Mainspring #718 for Hampden 16s, Factory No. 3696, steel, new in possibly frail envelope.  See images for precise mainspring specifications. I likely have several of these so the one you get may differ sightly 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.