The numbers/letters can tell you internal length, layout and the number of berths
The first three (or four) numbers represent the internal length of the caravan
Up to 1998 the length was shown in feet and inches e.g. 165 or 1650 = 16ft 5in
From 1999 the length was measured in metres e.g. 500 = 5 metres
After the dash or slash you may have numbers or letters
The number represents the number of berths
Letters refer to the layout i.e.
BB = Bunk Beds
CB = Centre Bed
EB = End Bathroom
EK = End Kitchen
ES = End Sleeper
ES(D) = End Sleeper Double bed
ES(T) = End Sleeper Twin beds
ES(6) = End Sleeper 6 berth
I = Island Bed