I am no expert, but I have been looking into aging deer on the hoof. Here is a good reference:

http://www.1atexasdeerhunting.com/bodyagingdeer.htm

When I look at him, I see minimal brisket, a swayed back, and a relatively slender body. I would guess at most 2.5 years old, although he could be an older 1.5 year old.