The drawing below reads "This insurance cover is from my personal space collection. Charles M. Duke Jr." What was an insurance cover?
It's an envelope (for letters, forms etc.) that was signed by one of the Apollo astronauts before their flight.
The Apollo insurance covers are autographed postal covers signed by the astronaut crews prior to their mission. The insurance covers began with Apollo 11 and ended with Apollo 16. The ability of astronauts to obtain much life insurance was limited, so they signed hundreds of postal covers before they left, on the presumption that they would become highly valuable in the event of their death.