Conversation so far:
When was the golden age of comic books?
the character's first appearance is usually given as Adventure Comics No.
40 (cover-dated July 1939).
Where else did he appear?
he also appeared in DC Comics' 1939 New York World's Fair Comics omnibus.
Who appeared with him?
CANNOTANSWER.

Question: What was special about Sandy the Golden Boy?
Self-contained rewrite: What was special about Sandy the Golden Boy?