The Model B Com I used to fly had a rear bench seat
...Then is wasn't a B!
)
It might have been a 250 or even an 'oddball' '65 260 but B's have individual seats in the centre row and two funny little squabs/press stud backs in the rear.
No doubt that they are fine machines but the B is a leap from the vintage technology to something that feels sigificantly more modern. A beautiful A model visited Popham today. I didn't get a chance to look closely but it was a jewel from afar. Nice new 'factory' scheme, too.
Hope you find the STC paperwork.