Rugo...
To quote the great musical philosopher (
) Paul McCartney...
Listen to what the Man Says...
If you have done your research and you find a mirror maker of the reputation of someone like Mark ... you can be satisfied you're getting a great mirror.
Reputations (at least in our hobby/pastime) are built on performance of mirrors in the real world, out in the field, and the subsequent word of mouth.
I'm sure those bits of paper serve as some form of comfort but they're no substitute for a trained eye and what you "see" through the eyepiece during a star test.
I'd say you're better off gaining a thorough understanding of how to star test and then being the judge yourself