Newall Security Mainspring #903 for South Bend 16s No. 27528 - Steel

Newall Security Mainspring #903 for South Bend 16s Movements, Factory No. 27528, steel, new in frail envelope. See images for precise mainspring specifications. 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.