There were a few ways to get a MKM .
One was to buy frame and body kit , and fit your own drive train and suspension. Four valve heads were optional.
Another way was to buy one one of the bikes commissioned by BMW - they had special and matching engine, gearbox and frame numbers, and always had the four valve heads. They are the definite MKM specials, and were potent, if short lived bikes.
There were probably a few other ways of getting one , including getting Mike and probably HPN to build you one to your spec, and these could be claimed to be genuine MKMs too, if documentation was supplied.
So before you paid big money for one you would want to know exactly what you were buying, as a matching number MKM is worth a lot more than a home made two valve kit bike.