Well in the aftermath of WWII the European and Asian economies were smashed and in attempts to recover the countries searched to products to export that they could make with limited industrialization as their industrial base recovered and hence earn "hard" currency. In many , UK, Germany, & Japan in particular, the economic planners set up the manufacture of lithographed tin toys as one of their recovery products. These could be made quickly, were popular exports, and took modest industrial facilities. Brimtoy, in the UK, was a pre-war manufacturer of toy trains and went back into production in the early post war period. In those days, it was hard to acquire the toys IN the UK as they were reserved (by Gov't decree) for export. The one below, is somewhat later than that very early period as it carries the "new" British Rail livery - the RR's were nationalized by the UK in 1948 - and the tender carries the famous "Lion and Wheel" logo of that period. So likely this variation dates to the early 1950's.
It is clockwork and made almost entirely of lithographed sheet metal. The cars try to emulate the "blood and custard" color scheme of the BR coaches of that period. She came to me from an auction and was complete with her full set box that included, interestingly enough, an oval of track that included a gated road crossing!
Here is the set as she appeared in her box. The short piece of track is to make up the straight line distance taken up by the road crossing on the opposite side of the oval (very good planning) and the box also contains her "key".
Best Wishes, Don