I searched and did not find a dedicated thread on this delightful pre-war Caravan. Year ago, I bought a blue and fawn version, that had slight fatigue and was quite scratched up. Then a couple of years ago, Keith Harvie had a much nice one for sale, so I acquired it. This one is chocolate brown and light tan or fawn, and is totally fatigue free, and the paint is in wonderful condition, very bright and shiny, but does have several chips.
I have never seen any documentation as to the real prototype, and since I am working on my own Dinky collection catalog, I decided to try searching for an image. Preliminary searching led me to pursue the "Royal Winchester" line of caravans, and I was able to find several images dating to 1935, that are very close to the Dinky version. It appears that they probably made these in several different models, of varying length, which would explain the minor differences.
Meccano first made it available in 1936, in several colors, and it was discontinued due to the war in 1941, and then never re-issued, as many other models were. Richardson's books state that later versions had the roof windows filled in; both mine show them still open, so not sure when that took place. Likely due to die wear.
The Dinky model shows what appears to be glass in the upper half of the door, and a closeup photo of a real one shows that they used leaded glass in exactly that same pattern.