The shorter air brake vans types VAA, VBA, VCA and VDA have similar bodies but with variations on door configurations - VDA having sliding central doors and hinged end doors. They also use similar underframes to other wagons being built at the time like the OBA for example. These frames have become donors for conversions to other types e.g. FPA. and reference to their number will show their origin.
Margam, 1985. Colin Baker (lokfuehrer@ntlworld.com)