Mayfair has a been a source for pinball parts for at least 20 years.
He was a baseline LONG before many others.
Most of the "old time" collectors have done business with Steve at one point or another.
So yes, he is the "real deal".
Be patient, he gets busy.
Backglasses, NOS or reproductions are stored upright in "slots" at his storage facility to keep them protected.
He has 1000s of glasses, if you ever get the chance to meet him in person.

Alan Meyer did the reproductions for the original Black Knight (with mirroring) and they are FACTORY ORIGINAL equivalency.
He also did Black Knight 2000 (also with proper mirroring) in prototype red lettering.
I have a AM BK backglass on my wall, that was my spare, when I owed my BK Limited Edition.
I also have a regular run BK 2000 on my wall (the one that was one my machine), that was a swap out signed by Steve Ritchie.
If you can find them at Mayfair, Specialty, or Marco, buy both.