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?