KBK Mainspring #3024 for South Bend 0s Factory No. 12528 - Steel

Kilb - Beck - Kuesel Inc (KBK) Genuine Factory Mainspring #3024 for South Bend 0s movements, Factory No. 12528, new in 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.