AB cigarette packs containing T206 cards with AB backs were the standard size as the other T-brand packs.
Furthermore, T205 cards with AB backs are the standard size (2 5/8" x 1 7/16") as the T206 cards (except AB ones)..
So, the mystery remains as to why the AB - T206 cards were cut narrower than the other branded T206's, or T205's, or T207's.
TED Z