The most interesting disc I've had sent to me for conversion to cd a while ago was one that was sent home from a second world war zone through the NAAFI in 1942, to a wife with a spoken message to her and the children from her husband.

It was a metal (aliminium)? disc about 4" across, sandwiched between a layer of shellac? on each side, one side recorded, the other smooth.

As it was starting to crack and a few pieces had broken off completely, luckily around the edges, the family wanted to preserve the message which I managed to cleanup and transfer to a high quality CD.

I now wonder if it will still be legible in another 70 odd years!