Are these pre-pro's ?

[Rob]

I cannot see yellow in the first photo that Steve shows above Reg, I see white, so am baffled a bit

[fixer]

We will never know what colour it is, I like Christian am assuming it would be a yellow taxi like the r/w impala as it states it's a taxi in the text just visible in the picture

[ChFalkensteiner]

Yes. That picture is a black & white picture, so we do not know the actual colour of the model pictured for sure. I just assume it to be yellow because of the word "taxi" in the caption, and because from that other picture on my website it is known that they had plans of issuing a taxi version and made prototypes to that effect.

Regarding the plain white Mercury models, I would say most of those are examples of the variation with Police labels (which was a regular twinpack issue) which lost their labels at some point, or maybe were produced by mistake without those labels being fitted.