I found out that the abbreviations RC, AT, PW, CD, and AG on record changer model numbers mean about the same thing:
RC means record changer (used by Admiral, Collaro, Garrard, and Motorola)
PW means plattenwechsler = record changer (German - used by ELAC)
CD means cambiadiscos = record changer (Spanish - used by Fonografo and Thorens)
AT means automatic turntable (Used by Garrard and Technics)
AG means autogiradischi = automatic turntable (Italian - used by Philips and Lesa)