The very first pic of the buck tells everything about him as far as age that you need to know.
The shape of his body is what's throwing me. He looks like he has a barrel chest/large neck but then it looks like he has a small waist...that's what's leading me to post mature. Most the deer I'd call 4.5 - 6.5 look more like this deer as far as body shape...If I'm wrong about this deers age please feel free to correct me as well:
Not all 5 yr old deer look like the rest of the 5 yr olds on the same ranch or area...same within every age class there will be those that are younger or older looking than the rest. Same with humans...especially mentally likes some clowns
If you ever get the chance to go to a deer breeder and look at pens of 1 yr old, 2 yr old or 3 yr old bucks you will see it first hand. Observing bucks like this is a learning curve you can't get in a hunting situation since in the pens you know the exact age....in the hunting situation you need history to get more accurate or years of aging deer on various ranches, then shooting them to verify. IMO, the first pic the buck has to much neck to be younger than a mature buck in the late summer, he has a lot of shoulder/chest mass, he is setting down on his hooves which to me is a sign of age, he has the hump over his shoulders showing in most of the pics and his face/head profile is that of a mature buck that is 5 or older. I have learned over the last 31 yrs to go with my first glance judgement on a buck as far as age. I have learned the longer you study a buck the more you can talk yourself into or out of an age class.