Here's the AFN 16-inch record alongside a standard-size 12-inch LP, The Jazz Combo from I Want to Live, 1958. I Want to Live was a 1958 movie starring Susan Hayward that had an entirely jazz score. I saw it at at the Idle Hour theater on the Frankfurt Army base when it came out. It was my first exposure to modern jazz and I liked it so much I went straight to the PX to buy this record. The musicians are Shelly Manne (drums), Art Farmer (trumpet), Bud Shank (alto sax and flute), Frank Rosolino (trombone), Pete Jolly (piano), Red Mitchell (bass), and of course Gerry Mulligan (baritone sax). I would see many of these artists in person before I left Frankfurt at the big concert halls and/or the Jazz Keller.

Long Playing records were not developed until 1948 and did not become popular until the 1950s. The original 1940s AFN records did not have microgrooves and could hold only about twelve minutes of audio on each side, whereas an LP could have about 15-18 minutes. Still, the early AFN records were indeed "long playing" in comparison to the dominant 10-inch 78rpm record which had room for only about 3 minutes of audio per side. By the time I worked at AFN in 1959-61, the 16-inch AFN records did, indeed, have microgrooves and popular music records typically had 10 or 12 cuts per side, 20-30 minutes of music.

Read more about the development of phonograph records in Wikipedia.