I'm guessing a 2.5 year old. It appears he must have had some damage to his antlers when the antlers were growing. Causing the lack of headgear. Based on the belly coming up near his rump, thickness of neck that's how old I think he is. The "spike" on his right, I believe is what his brow tine would be right now if the rest of his rack wouldn't have gotten busted. Maybe he got hit by a car earlier this year or something. He has pretty thick bases on busted off antlers. Who knows what his antlers would look like right now, if he actually did get hit by a car. So with all of that to think about, I think he's no older than 2.5 years old. But he did get hit by a car or something else when his antlers were growing. Or perhaps he got his butt kicked after his antlers were out of velvet, there is that chance, just looks like they were busted a while ago, from what I can see.
The face is too compact for me to believe it is any older than 2.5 years old.
Edit: JPH, I'll arm wrestle you! If I win, it's 2.5 years old, if you win, it's whatever you want it to be!
Even if it is 3.5 years old, this buck is going to be a monster next year. Like the old saying goes "You should see what the other guy looks like!" That's the truth in this one I think.