Included with this lot is a letter of authenticity signed "Al Worden" on his letterhead that gives a precise explanation of the history and purpose of these insurance covers. It states (in part): "I hereby certify that the commemorative postal cover, number 31, included with this letter is an Apollo 15 insurance cover. It has been in my possession since the Apollo 15 flight in 1971. The NASA Manned Spacecraft Center Stamp Club in Houston, Texas provided these covers to our crew. They were signed by us before the flight, stamped, postmarked on the day of the launch, then held by our families during our flight. The purpose of these covers was to provide each crewmember's family with a type of insurance in the event that we did not return. There was no other insurance available to our crew because of the risk of flights to the moon."