I don't doubt your word, Steve. If you say you're 100% certain you've seen it, you've seen it.
The answer to the riddle may lie in the date of the drawing, in that my use of the number 8 when we came up with the designation CMN8 was purely because I thought - at that time - that if we were building the car after CN7, it logically had to be called "CN8". Of course, that was stupid of me, because the earlier designation, CN7, had nothing to do with that car (the Proteus-engined LSR-breaker) being the seventh Bluebird. It was a reference to the fact that the final design chosen for construction was the seventh in a series of potential concepts for that car.
Going back, then, to the car that Norris Brothers and Donald announced, through the Plimmers publicity agency, in 1965 ... the car was definitely not referred to in their literature as CN8. I say that because Ken himself gave me that literature back in 1974 and I still have it. But, of course we have it from Leo Villa's book, The Record Breakers, that this car concept was called Bluebird Mach 1.1.
You are right to say that the original design of Bluebird Mach 1.1 had a more rounded nose. The nose got more pointy much later, when a fellow named Greville Dawson, whom I'm still in touch with, got a windtunnel project under way and attempted to resurrect the project - in the period just before I did, in fact. (I have that windtunnel model here in my office at home, not four feet from me as I write this.)
It would be great to see your document, Steve. I don't doubt your word. But I do doubt the use of the number 8 by the Norris Brothers, as it makes no sense. That car - the supersonic concept - wasn't the eighth of anything.
But Ken may have picked up on my CMN8 designation at some point and abbreviated it, on his own personal paperwork not for public release, to "CN8".
As I say, the figure 8 means nothing in relation to that car (the supersonic car). The eighth what? It's an irrelevant figure.
At some point I'll invite Greville Dawson to write a few words about his involvement with Ken and the Mach 1.1 concept (1973). It has never been brought out in the public domain and it really should be, for posterity's sake.
All the best.