As a trader of dinky toys, I often found it difficult to distinguish whether a model was pre or post war. (ie. before or after 1939/1940)
This is especially troubling when the production period of a model ran through the war. It is of course iportant to know what you are selling so that you do not 1) sell for under value or 2) misrepresent your item.
Here is a little trick to distinguish between the two: without exception, a pre-war model will have thin axles. This is the only guaranteed way to know whether your item is pre-war. It is a good idea to keep a pre-war and a post-war model in your collection to compare the axles of new additions.