I'll play. That is definitely a mature buck, despite the headgear not being great. Here is my hunch: given the deep brickekt and paunch, heavy body plus what looks like fat pockes on his underside, etc. I think it's possible this buck may already be past his prime, which means he could be as old as 7.5 or more. I love to see that one aged after you shoot him.
And then I could be completely out in left field. i.e.He could be just 4.5. I sure don't think he could be any younger than that.