Tri-ang Minic Motorway

Red Rolls Royce
please click on images for full size photo

The  fabled Red Rolls Royce, has often been mentioned but it has been difficult to obtain any photos until now. The item above with the provenence below (I think courtecy of CBtoys, now confirmed as being originated by Chris Bugby, thanks Chris.) shows one of the Rolls Royce models in Red something that was thought never to have been put into production. This model was taken as being a very rare prototype with a trial extrusion using whatever spare plastic colour was available, in this case Red. Standard practice with Tri-ang test models.
However, recently, April 2024, a contributer to the Minic Motorways Facebook Group posted some images shown below. Yvan Latrobe had bought a Minic Motorway Set on the US Ebay some 13 years ago.
The M.1501 A/US/R Set contained two Rolls Royces, one in Red, and the other in Light Green.
The British M.1501 Sets A/B/C only had one vehicle but the same track as in this Set. US being United States but did the R stand for Rolls Royce.
The interesting thing about this model is that there is no molding/line on the bonnet dividing it as the original and subsequent models and the front window surround is much thicker. We thought, could this be a repaint or a copy?? However, Yvan then sent photos of the underside!!
On closer inspection of the Chassis it can be seen that there is no engraving/stamp of any wording but there are signs of tooling/filing on it.
So no doubt in my mind that this is a genuine model but an early prototype.
So how and why did it turn up in an American Set?

Many photos courtesy of Yvan Latrobe