There's some weird things going on, and it never made it to production? These alloys are devout of any markings. As far as we know, they've never been mentioned by anyone associated with Rover in those days yet they're fitted to P8 and P9 full-scale clay models.
Funny thing, while researching AE Brico fuel injection systems I went to British Motor Heritage at Gaydon and categorized a bunch of pictures they have on file, without looking at them. They only provide a RO number and a brief description. Usually it says something like 'Director's car, P6B - William Martin-Hurst' or 'Experimental suspension P8 Programme'.
A thumbnail size picture is 5 GBP and an additional 10 GBP to get a high resolution image. I did that for a while, finding amongst other things pictures of my own car (JXC813D). One of the other things was a car licensed as NXC22H. The wheels.. it bothered me for years. Italian? Bespoke? P8 and P9 can be seen with them in Bache's design studio.
HXC659H is actually nothing. It's not registered as such, but just something they put on a clay model.
Now, I bought the probably one remaining set. They popped up on eBay last year, Chris Wilson bought them quickly and then I got them from him. The owner told Chris that he paid over 2000 GBP for them back in the early eighties, bidding against none other than Mike Beetham, the former chairman of the P6 ROC.
So, in the near future, there will be a P6B in Canada with some very weird wheels. Let's see what happens.. could be fun! Do you have any information? Please share so in the comments or send us an e-mail!