Did you know that on the 3rd day of December 1948, the brand-new format is proclaimed by RCA in a front-page feature in Billboard magazine? The first publicity of the 45s arose the subsequent March.

The records came in seven glassy colors, one for each type of music:

dark blue = light classics
light blue = international
yellow = juvenile
bright red = folk
deep red = classical
green = country
black = popular