I have asked a man who knows and he told me that the car is chassis no ‘1934’, but that this car does not have a continuous history and was built up from a few assorted bits in the late 1960s. ‘1934’ had a side valve engine until 1926, when a twin cam 16 valve unit was fitted. It still has one of those, but whether the same one as that fitted in 1926, we do not know. He agrees that the wheelbase appears to be that of the short chassis, but does not know whether this is as it was in the first place, or whether it has been built up on a shortened long chassis.
Can of worms, I'd say
Oh and he reminded me that not only did Bamford and Martin call the cars "Aston-Martin" but it was spelled with the hyphen in their day.