This is a lenticular 3D postcard showing a space walk. The description on the back is as follows:
At a speed of 5 miles per second 120 miles above the earth, the astronaut is connected to the spacecraft by a 25-foot long gold-plated umbilical line which provides communications and oxygen.The stamp on this card commemorates the Apollo 11 first moon landing. This 10¢ air mail stamp was issued on September 9, 1969. The Cape Canaveral cancellation on April 14, 1970 relates to the Apollo 13 self rescue which is briefly described by the cachet stamped on the lower left.
Here is some information on the Apollo 13 mission from Wikipedia:
Apollo 13 was the third Apollo mission intended to land on the Moon. The craft was successfully launched toward the Moon, but the landing had to be aborted after an oxygen tank ruptured, severely damaging the spacecraft's electrical system. The flight was commanded by James A. Lovell with John L. "Jack" Swigert as Command Module pilot and Fred W. Haise as Lunar Module pilot. Swigert was a late replacement for the original CM pilot Ken Mattingly, who was grounded by the flight surgeon after exposure to German measles.
The mission was launched on April 11, 1970 at 13:13 CST. Two days later an explosion crippled the service module upon which the Command Module depended. To conserve its batteries and the oxygen needed for the last hours of flight, the crew instead used the Lunar Module's resources as a "lifeboat" during the return trip to Earth. Despite great hardship caused by limited power, loss of cabin heat, shortage of potable water and the critical need to jury-rig the carbon dioxide removal system, the crew returned safely to Earth on April 17. NASA called the mission a "successful failure".