KBK Mainspring #3904 for Hamilton 18s Factory No. 232 - Steel

Kilb - Beck - Kuesel Inc (KBK) Mainspring #3904 for Hamilton 18s movements, Factory No. 232, new in envelope. See image for precise specifications. Not very familiar with the supply house (would love to find them in a catalog) and it does say "Genuine Factory" so they may have just repackaged Hamilton factory mainsprings for redistribution to jewelers and they look like a really nice mainspring. 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.