Demonstration disk?

I believe that every such complimentary or free record destined for reviewer or radio station was an early pressing because sent out earlier than retail sales release date.
I don't think I am being too simplistic thinking of these routinely representing early pressing samples.
Having listened to early and later pressings one may find the "later" sound equal or "better."
Due to manufacturing variability any particular single vinyl record may turn out to be a fine sounding example.

Demo Lps with special labels started in the 1940's.. were very common in the 1950's and 1960's.. Used both as radio station fodder, and in-store demo disks. As time progressed the practice of printing special labels disappeared and by the 1980's no company made a special label for the DJ crowd. They mostly went to stamps on the jacket, or circles punched out in the barcode and cut-off corners on the cover.
A demo label LP is worth about 10% more than a normal LP. Though some with different color vinyl and special added features can be worth far more.
Stamped covers have no added value.

Thanks a lot. Always good to fill in some area that previously I had no idea was vacant!