BTs,
It was brand spanking new Mk2 B. They kept a set at Boscombe in pristine condition for trials. going by the other pics in the series it was around the same time as PURIBAD was being developed at Boscombe with AML. If I feel brave I will post the others in the series.
After a few weeks in the hands of some and with repeated bashing with the 10K tie downs all the drop nose pins were knackered and the floor pegs bruised. 30 years later the rollers were in better order than the yankee stuff 10 years on.