The English style mouth was made popular by Len Insull. Most all the pro vents from England used this type figure. I also believe that the mouth movements with the English figure are just as visible as the slot jaw.
A perfectly working Insull lower lip opens wide enough to show that the mouth is open and in conjunction with the upper lip I feel that the look is about as real as you can get for a dummy showing those great white teeth.
Craig Lovik back in the early 1980’s coined the phrase “Living Mouth” which is the English mouth but he was not the first American builder to do this style.


