Hi all!
I've used the word dapper for a very specific type of man, any age, similar to what's been said but to be dappper he must also have a certain je ne sais quoi, a certain verve, or simply a man who looks well put together, has pride in his appearance, perhaps a bit of a rogue with a twinkle in his eye.
Strange but I've never used the word in reference to a tall man (over six foot.) Dapper men, to me, are always shorter than average up to medium height.
In any case when I use it I always mean it as a compliment!