Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Quite certain that D12 is original from Wilesco, and made as a dealer special, to be used as an eye-catcher...or as a special order.
Leaning more towards the first, since several models was made this way, special orders usually is limited to a single model.

I have seen a few over the years with the exact same copper/chrome scheme, and actually own a D20 in that "dress" myself.