I believe basal circumference (and/or diameter as well) is the antler measurement that most correlates with the deer's age. In other words, of all the things about antlers, this is the single measurement that would give the best indicator of a particular buck's age. But I've seen several 2 1/2-yr-old TN bucks with basal circumferences exceeding 4 inches (most are closer to 3"). Meanwhile, many 4 1/2's will not break 4 inches, so as an aging mechanism, it is much less accurate than looking at the teeth.
It would be relatively "rare" (in TN) for a basal circumference of 5 inches not to be on a buck at least 4 1/2 years old.
You can somewhat guess basal mass by comparing the width of the antler (at about an inch above the hairline) to the width of that buck's eyeball. If the antler appears wider than the buck's eyeball, probably over 4" wide, then high probability that buck is at least 3 1/2. If the eyeball appears wider than the antler, high probability the buck is younger than 3 1/2. This assessment can typically be done very easily, very quickly in the field, and is often the single criteria I use in deciding to take a particular buck or letting him walk.
Another antler measurement that correlates somewhat is main beam length, which is much more difficult to guess in the field.
Meanwhile, antler "spread" does not correlate so much, as many 2 1/2's will be wider than many 5 1/2's.
