Oh the gravy train how sweet it is. The record labels give free copies of almost any release to radio stations (also to retail press etc). The tradition is as old as radio, while the some try to argue the opposite presently, at least historically RADIO SELLS RECORDS. So record labels are very willing to create ample opportunity for airplay, not just with the traditional gifts of booze, drugs and money but also with items of actual promotional value such as concert tickets and extra copies of a release.
I was lucky with this Decca promo. not only to I have the artist title and release date, I have a hand written date that preceeds it's commercial release by a few months. The promo copy below is more than 50 years old. In April of 1953 RCA was pushing Eddie Fisher hard at radio and TV. They got Eddie a TV show on the NBC network "Coke Time With Eddie Fisher." He scored two singles that year "With These Hands" and "Just To Be With You." In 1950 labels were already making exclusive promo-only pressings of records. Notice the number stamp 11840. Does that mean there were almost 12,000 promotional copies serviced? I'd actually bet it was more than that. (I think the initials E.R. belong to a promoter...)
As the RCA Victor LP implies, promo copies used to be labeled as such. Many of these lacked the obvious markings above and instead used a plain white label. These are highly sought after by collectors. They are often pressed to a higher quality of vinyl and are limited by nature. I have a few myself.
Around the mid 1980s labels began to punch out, mark, stamp, or cut-out their stock for promo. It lowered costs, but they are uninteresting to collectors in general. Of course this has another side effect. Selling them used has become all the easier. Thus creating a secondary market in used goods for which the label was never paid a retail margin. So did it actually save them any money? Nope. They were better off before with the clearly marked promo copies as below. This Bishop example is interesting because they were a pressing plant and not a label. They pressed for Session and SD records. Today radio serviced copies are ripped to a database and then sold off by impoverished interns. Already some labels are servicing music to radio in a digital format. With centralized playlists and satellite fed programs this becomes even more appealing. But the promo-copy practice continues. Their newest tactic? Lawsuits. Some online retailers have begun cooperating with labels and are removing promos from online sale. More here.