From phillip holmes: "... I guess the only giveaway would be
a unique matrix that couldn't be found on regular issues..."
The matrix would probably be the same. I don't know how you could tell
something was one of a run of ten test pressings or one of a run of a
hundred promo copies.
The acetates we and Atlantic cut were from the master tape using exactly the
same setup as the master disk. That's closer to the original than any
pressing! It was a singular experience we mastering engineers talk about
because it virtually always required pulling an all-nighter!
Bob Olhsson Audio Mastery, Nashville TN
Mastering, Audio for Picture, Mix Evaluation and Quality Control
Over 40 years making people sound better than they ever imagined!