James Whitmore was 26 in The Undercover Man when he played the character 'George Pappas'.
That was over 75 years ago in 1949.
This was his first recorded movie acting credit (although may not technically be his first actual acting role).
In 2009 he died aged 87, starring in 77 films in his career, 76 of those after The Undercover Man was first released. If he were alive today he would be 102.
In The Undercover Man, I think James Whitmore looks: