KBK Mainspring #3033 for Seth Thomas 16s Factory No. 2106 - Steel

Kilb - Beck - Kuesel Inc (KBK) Mainspring #3033 for Seth Thomas 16s movements, Factory No. 2106, new in envelope. See image for precise 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.