Of course there are ways to precisely calibrate such things, but is it worth it to set up instruments far more expensive than the only you're trying to fix? Been there, done that. I'm nitpicky, but at a
certain point, things can become overkill. Some of these magnifiers had paper shims in the base as
well as under the mirror. All it takes is a little bit of sloppiness in either and you've got an issue.
In most cases the casting aren't precise enough to dispense with the need of some manual adjustment during final assembly. And I never ever assume that a piece of equipment is precise without first checking it - well, maybe a machinist's quality instrument from Starret or Mitutoya
accompanied by a regiesterd certificate of accuracy - and I they'd have made on of these devices
it would have cost a lot more than what you paid for Peak. In fact they make instrumentation which
will read that front surface mirror and make a countour map of it several feet wide in millionth's of
an inch, just in case you need to see how flat it really is!