Summer necks are expected to be small but he has the teeniest neck ever. Same with the rack. Legs are real long compared to body. All that says young but his body actually has some thickness to it and he has some hock stainage. Hes not your typical looking deer for sure so its hard to say. At least 2 but hard for me to call him 4. Curious to see more pics and especially later on.
That is the quandry. I originally thought post mature and on the way down but looking further he does look younger. Also he is smaller then the other bucks so leaning younger now as well.
Smaller body does not always mean he is younger. Some bucks are orphaned as a very young fawn and they may be able to barely survive. If they do survive the result is they are never large bodied as other bucks their same age class. I killed a very old post mature buck in South Texas one year, he field dressed either 75 or 79 lbs. He had no teeth left in his mouth and was a regular at a protein feeder. He looked his age up close on the ground but not at first glance in a trail cam pic. When I saw him person I knew right away he was very old. Mature bucks on this ranch would field dress from 165-195 depending on the time of the season they were killed.
The buck in the pics above is not in the mold of a 1.5 yr or 2.5 or 3.5 yr or etc age group. The big white rings around his eyes is what is throwing me off. His thicker body is another thing that makes me think he is a bit older than most think. Majority of people look at the antlers and think young deer. His neck line is more of a 2.5 yr old to 3.5 yr old...but if he is a runt for his age class then that will explain the smaller neck.