Here is what I can tell you. It is as much attitude and posture in my observation. Unless you have been looking at them for a while it's tough. Most folks seem to be amazed at how small the bear is they shot.
Think "human" when judging bears. They live a long time and continue to grow long after maturity. Take my wife for instance ( I need to lock the door BRB )
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. As a newly wed she was similarly shaped as she is now but, how should I say this, less so.
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Attitude, yes she has definitely gotten one of those worthy of a mature mom. So what we are looking at is a gal with a broad butt, heavier in the middle, though still weak through the shoulders and fairly fine features through the head. The scales do not do her justice, weighs more than she looks.
A boar on the other hand will have attitude pretty early, well muscled and athletic looking. Puts me to thinking of a Cassius Clay, obviously strong and athletic, but when push comes to shove, mostly mouth and bluster. With maturity comes the Mohamed Ali. Strength, smarts, efficiency of movement (lazy even), overweight. Not exactly athletic anymore, but certainly not to be trifled with, he is the king of his world and acts like it.
To my mind the head and shoulders tell the sex story. Attitude, and posture gives away the maturity and help in size evaluation. Lastly, I would think twice about pulling the trigger early especially if you are adamant about wanting a large trophy. Think 55 gallon drum size body, not how high up the back is against some tree, they get tall before they fill out.
Now I will admit where this is coming from. I have a rug from a three year old boar, 6 1/2' from nose to hind foot, weighed 240#. it made a very nice rug most folks are pretty impressed with the size (or very respectful of a hunters pride). I recently shot a nice sow she was 300# recently got confirmation from the Ontario MNR that she was 8yrs old, I was pretty impressed. This girl went to the taxidermist came back a half body mount, HOLY SHRINKAGE bat man. Shoulders are what you mount, not belly and butt. Keep this in mind when you decide how you want to preserve your trophy.