Richard
I have collected American Beauty T206's for over 30 years, I have 44 - AB 350 frame....18 - AB 350 no frame....and, 70 - AB 460 cards.
My guess is that American Litho started cutting the AB's thinner in anticipation of the narrower AB packs. It's my understanding that the
narrower (8-cigarette) American Beauty packs were to be introduced sometime in 1911.
Widths of the AB cards vary all over the place. This Davy Jones is the "fattest" of my AB cards (exactly the width of a normal T206 card).
..
v.................... 1 7/16" ......................v

.
While AB 460 cards cards tend to be the narrowest......

.
TED Z
.