KBK Mainspring #3836 for Elgin 4/0s No. 4789 - Steel

KBK Genuine Factory Mainspring #3836 for Elgin 4/0s movements, Factory No. 4789, steel, new in envelope. See images for precise mainspring specifications. Not very familiar with the supply house (would love to find them in a catalog), but it says Genuine Factory and indeed the spring is marked E.N.Co on the end. I specialize is hard to find watch parts so I usually have whatever you might need and all watch parts are unconditionally guaranteed. Images do a pretty good job of representing the item.