Thats awesome. I have a similar story, where I was removing the gas tank from my 63 catalina, and while messing with the gas cap, I found one of those black magnetic key holders inside the quarter panel behind the gas door. Sure enough, it had an almost new brass ignition key. Now I have 2.
Not as shiny as yours though. Now if I could just find a copper 1943 penny under the seat somewhere...