KBK Mainspring #3909 for Hamilton 16s Factory No. 534B - Steel

Kilb - Beck - Kuesel Inc (KBK) Mainspring #3909 for Hamilton 16s movements, Factory No. 534B, new in envelope. See image for precise specifications. Not very familiar with the supply house (would love to find them in a catalog) and they clearly are "Genuine Factory" (see the last image) so they would be 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.