Im gonna say at least 3 1/2 but more like 4 1/2.
The teeth is a good aid but not the only one, the body of a deer along with the teeth are more accurate. that body is no 2 1/2 year old. The wrinkles on his ear show age. His head shape also tells me he is older than 2 1/2 . that neck is no 2 1/2 either. His legs are thick also. Im gonna stick with him being 4 1/2 yrs old.
I also kinda of dissagree with those links. that 5 1/2 is more between 7 and 9 years old. They are also showing to much wear within a year.I dont believe it's that drastic. but hey thats just my opinion.