My dad worked for North American Aviaton/ Rockwell/rRocketdyne in the 50s and 60s. He worked on the X15, A5, XB70 and the space program until it went kablooey after Appllo. He also worked on ICBMs. They had some exotic alloys, naturally, as well as some surprising non metal shields, nose cones and the like. ICBM warheads have to endure extreme temperatures and pressures on reentry
Rocketdyne made all the head men and their wives simple, shiny alloy rings. The metal, whatever it was, had to be sized at the plant. Only a diamond can cut it and darned slowly at that. Engraving their names on the ring took a week per ring and costs one diamond bit per ring. Mom and Dad both were buried with them
Dad once said it was a tungsten-carballoy-titanium-beryllium alloy with some other exotic metals added in. It had been through a launch, orbit and reentry cycle which really toughened it. Before launch it had been cryo-treated, too. I wish I still had them but they were buried with my parents. They never had a scratch and looked like polished silver or stainless steel. They were also amazingly light.