Probably is a boy but he's a light color. Looks pretty young...maybe 4 mo as looks like stripes just disappeared.
Has black baby eyes but not sure exactly when they get the lighter ring & some mutations eyes stay black. My English spangle never got a grey iris but she died at about 1 year. When I got her they really did not know age but she had lost the bars on the head so we always thought 4 to7mo but she must have been closer to the 4mo as in 5 mo later she still had black eyes.
Not sure what mutation but not a regular one & feather pattern on back is different.
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?