SOUNDNESS EVALUATION

100-Age,add 5 points for every year different than advertised

Here again, I am going to try and simplify. What you need to identify on the six lower front incisors are dark colored indentations or "Cups" that appear, and then disappear, as the horse ages.
As the horse grows old enough to shed his milk teeth, these cups appear on the permanent incisors that erupt in the center.

Or, for a two/three year-old, two cups showing as this:

At four years-old, he has four cups showing:

At five years-old, he has all cups showing, and is termed Full Mouthed as all the teeth are now permanent:

Note: At five years, on male horses only, a set of Canine, or Tush teeth appear behind the Incisors.