Promotional copy - any different in sound quality?


I wonder whether promotional LP copies "not for sale" were made any different leading to better sound quality. Are they any more worthy than non-promos?
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Sometimes, but not always, the promo copies come from earlier in the pressing run with an earlier stamper and earlier in the sequence off a given stamper. But there is no guarantee and no consistency about this. I won't pay a premium for a promo copy, but I'm always willing to give one a comparison listen just in case.
The 'promo' really MUST hace a promo (special, different) label to have any value.
Earlier years of LPs had plenty of special label promos.
(for example: Columbia records has a white label instead of the red label..)
A few promo records even come in special vinyl, blue or red.. etc. Or are made from "QuiexII vinyl" from the 1980's on.
The special label promos DO come from the beginning of a pressing, and are more valuable because of being rare. (not because of the sonic superiority, except the "QuiexII" which ARE significantly sonically better.)
When you find a bunch, usually they came from a DJ stash, or a radio station, and are like new.
The later (1970+) promos are mostly just a stamp on the jacket.. which is of no value whatsoever. They are the same records from anywhere in the production run.. and are stamped 'as needed'.
Yes, the promos are much better. I have spent enough time comparing the promo and non-promos of the same. The results are always the same. However, promo copies are often not in good condition.
Most of the WLPs I have are CBS (Columbia/Epic). The ones from the late 50s and early 60s are pressed on quieter vinyl than the standard issues. Same thing with the Mercury promos I have, except the promo labels on these are either gold or sort of peach-colored. I have a few 70s CBS promos too, which have white labels, but don't seem to be of any better quality than the regular issues.
I have a large collection of White Label Promos (WLP)that I have purchased over the years. My view on the sound quality of these promos has changed with the passage of time.

Up until recently I felt the WLP were superior sonically but as my system got better and my record cleaning techniques improved, I use the Walker Prelude record cleaning system, careful listening comparisons with many original pressings of the same record indicate that the WLP do sound on average a little better than the average vinyl pressing but if you acquire 4-6 regular copies of that same record the Promo copy rarely wins in the shoot-out. I no longer look for promos of any kind anymore but instead just look for clean originals and evaluate each copy separately.

Johnny
I still love to play my 6 eye columbia Miles Davis Kind of Blue. Its only better because its the first press of a great classic and still plays wonderfully.
I HAVE A FEW PROMOTIONAL COPIES OF RECORDS, ALL ARE 45 RPM'S. MOST SOUND JUST LIKE THE THE FINAL RELEASE BUT SOME DON'T. I ALLWAYS FELT THAT THESE ARE WORTH HAVING IN A RECORD COLLECTION BECAUSE THERE ARE FEW OF THESE IN EXISTANCE. SOME OF MY PROMO'S CAME FROM RADIO STATIONS AND EVEN HAVE THE STATION CALL LETTERS OR OTHER INFO WRITTEN ON THEM. PROMOTIONAL RECORDS ALWAYS GET MY ATTENTION AND I GRAB THEM WHENEVER I CAN.