What a beautiful bird !
The leg band will usually show the breeder's or aviary initials, the location he was hatched (State or province abbreviation), the year it was hatched, and the chick number for that breeder. It usually will not show the month it was hatched.
This little one looks to be less than 4 months old, since he still has baby bars on his head. His eyes will develop the iris ring at about 6-12months old.
Mutation : Sky Blue, Yellowface II, Greywing.
The Greywing mutation is what is making his colours diluted, as this mutation will lighten up all his colouring by about 50%.
do you have any more pictures from the front and back?