ukinsurancenet.com has a great article about Astronaut Insurance Covers. These were basically postcards signed by each member of an astronaut team shortly before launch and then if something bad were to happen their families could sell these at a high price to act as a strange form of life insurance.
An Insurance Cover from Apollo 11, postmarked July 20th 1969 and signed by Neil Armstrong, Michael Collins and Buzz Aldrin
You can read the entire ukinsurancenet article here.