When in an antler restricted GMU, I've always been a brow-tine counter (which varies by unit)...and even that sometimes gets tricky. It's soooo much less stressful in an any bull GMU!
That said, I'd say he's over 50"...but when behind a rifle or bow and in doubt, just pass.
Generally speaking, all things being equal, fingers crossed...I count the distance between the eyes as 10", and if the length of the beam on each side prior to brow-tine palmation is equal to the distance between the eyes, then the probability of reaching the 50" goal is considerably higher....but, but, but...
Geez, I'm getting stressed just posting the above comment ABOUT judging 50"...and I've hunted moose in Alaska for over thirty-years!
("any bull GMU, any bull GMU....breathe....any bull GMU....")