Wyatt Earp
Probably few people now realize the real Wyatt Earp lived until 1929. I've seen pics of him late in life and he looked good for someone in his late 70s. They really didn't have to apply anything to Hugh O'Brien to make him look older than the character he was playing as O'Brien was past 70 himself.
I haven't seen the film but if it takes place in 1914, that would have made Earp age 66 at the time, not what you'd call an old man quite yet.