Conversation so far:
When did Rocky Graziano begin his professional career?
As he grew older and seeing no other way to raise his standard of living, Rocky Graziano signed a few boxing contracts.
Did Rocky Graziano have a professional boxing career?
Rocky Graziano signed a few boxing contracts, but the rigors of training disinterested him.
How many championships did Rocky Graziano win?
At age 18 Rocky Graziano won the Metropolitan A.A.U. welterweight championship. In 1947 he became world middleweight champion.
Did Rocky Graziano have a trainer?
No.
Was Rocky Graziano easy to train?
The rigors of training disinterested Rocky Graziano.
Did Rocky Graziano win any medals by boxing?
Rocky Graziano fought four matches and ended up winning the New York Metropolitan Amateur Athletic Union Boxing Competition. He sold the gold medal.

Question: When did his professional career end?
Self-contained rewrite: When did Rocky Graziano's professional career end?