I was thinking about this after watching THE NICKEL RIDE, where Jason Miller plays what is supposed to be an aging crime boss while he himself was in his mid-30s. (George C. Scott was originally cast in the role.) Somehow, Miller completely sells it despite no visual attempt to age him up. Through performance alone, he just seems that worn out.
In the other direction, Margarita Levieva is playing a character fifteen years younger than she is in THE DEUCE, and you would never know that without looking it up. It's outright scary.
What are your examples?