Richard, the Workshop body was fitted to many Ser 2A's (both early and late styles) and some Ser 3's. While the basic form of the body was the same, there were lots of different variations to the actual fitout of both the Truck body and the Trailer to suit various applications, ie: Armourer's workshop, lube truck, welder, instrument repair, etc. The
REMLR Fleet Information page suggests that there were 437 workshop trucks in 14 different versions. The Trailers were fitted out in a similar number of variants! I have owned both a 2A Workshop and a Workshop trailer (which I still have)