Kilb-Beck Mainspring #3016 for Hampden 3/0s No. 9696 - Steel

Kilk-Beck Company Mainspring #3016 for 3/0s Hampden movements, Factory No. 9696, steel, new in envelope. See image for precise mainspring specifications. Not very familiar with the Kilb-Beck supply house and would love to find them in a catalog somewhere. 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.