a respected hunter/friend thinks this deer has an edema - an injury that causes his brisket to swell and fill with fluid - that is what is causing the neck to look so different - all the other indicators of head, back and belly show him to be young

I love learning new stuff about deer - never heard of an ednema but in this case it makes sense

if he is called mature (6.5) and he turns out to be younger there is no issue with the hunter - but we are very conservative and if there is any question at all we pass until next year - our history shows that overall when we pass on a deer we are not certain on then good things happen

Tim,
I have a buck on my lease with a very similar body condition (-20" antler), with the same brisket scenario but have a little more history on the deer. I'm pretty sure the deer I have is a 5 yr old based on what we knew of him last year. In early oct. this year he showed up with a large swollen abcess between his front legs with swelling that carried up his lower neck slightly. This swollen area ruptured and began to slowly diminish about 2 weeks later. He still has some swagger in his brisket similar to the deer in your video but it seems to be slowly disappearing, however he is also now bulking up in his neck region as are the other mature bucks.
It very well may be the deer in your video encountered a similar situation (snakebite, thorn, ??).
I would disregard the abnormal appearing brisket and age him based on other characteristics. He looks 5 ish to me but at the very end of the video I noticed he may have had a little loose skin under his jaw however this could still be attributed to the brisket condition and lymph response.