Can't imagine anyone younger in that division winning gold. Does anyone know? He was aged just 20 in a division of big experienced men. Fantastic achievement
Teófilo Stevenson was twenty years and 165 days (birthday March 29th, gold match September 10th). Wladimir Klitschko was twenty years and 132 days (birthday March 25th, gold match August 4th). Wlad was younger, and would have been (barely, by four days) even if his Olympic finals had taken place on the same date as Teófilo's and not over a month earlier.
It's hard to imagine anybody much younger than the age of 20 winning a Heavyweight world title or Superheavyweight Olympic Gold. Maybe 19 would be the lower limit. Though some people say Tyson was ready at 17 to win a HW title. Nah, no he wasn't.
The youngest to ever compete at the Games was Ben Bril, on exactly his sixteenth birthday and that was 95 years ago. That probably wouldn't be allowed today. I could maybe see Wlad's record being broken by a 19½ year old if anything.