I did the research and found evidence that, even though this A DoDo’s Evidence of Solo appears to be comedic, it is, indeed the certificate for completion of first solo flight:
“This is an important day in a pilot’s life, when a person symbolically gets off the ground and sheds his or her image of a flightless bird.”
The story Daddy or Mother told me is this:
Daddy was flying along on his first solo flight when the engine quit. He said, “God, if you’ll let me live, I’ll never fly again.”
The engine started back up, and he never flew a plane after that initial solo flight.
Note: The added scribbling is attributed to a small boy whose name, we believe, is Junior.