There's nothing special about the components on these, but there is a much earlier development model in existence. This used to be in a Belgian collection which was sold off years ago. I lost track of this item then.
I think even the dropside body was plastic on this one. Certainly only has a partial chassis component, and yet more different lettering. Would love to find it again and add it to the fleet.
Would be nice to track it down again and even better if you could add it to the collection, but there's a certain Mr Mick Flack out there somewhere, who I expect would be wanting the same...
The prepro looks much better than the production model in my opinion. No steam wagons have grey tyres, and the silver painted boiler is more accurate as boilers on the real machines are often painted with aluminium paint. The decals were too complex for the tampo process I guess, and I suppose the 8 spoke wheels are stronger than the 5 spoke examples on the prepro.