A fitting word/description for a person who seems more mature in appearance than most people his age?

I'm trying to describe a person who is young (in his youth 19-24, past teenage years) who at a first glance might look mature or wiser for his age. But if you talk to him you get to know him as a little naive though only in experience but not in wisdom.

So I have a description like "His face is calm and impassive and combined with his white hair makes him look wiser than 19"

• Can I use a word or phrase that can define this kind of person without giving away details?
• And is the description even correct to explain this kind of person?

Older than his years may fit, applying both for appearence and mind.

Example 1: But he’s only 38! Colin Farrell looks older than his years as he shows off scruffy beard on way to yoga class in Santa Monica.

Example 2: All this profuse, indiscriminate reading helped to educate him and to give him the air of a "wise child," older than his years and familiar with the ways of the world.

Sometimes, one will hear the term "old soul" for someone who seems to demonstrate wisdom that beyond their years.

The term precocious is applied to a person who develops skills or characteristics much earlier than usual.

If the person has white hair, they might be termed "venerable", or even better (rubbing in any disparity between their looks and their acts) "venerable-looking". Like, for example, in the title of this dissertation.