I just received the Tristano, Konitz and & Marsh Mosaic box from Freejazz (great service btw) and noticed that the first session from June 11, 1955 is in stereo. The next session in stereo is from December, 1957. Not remarkable in that (IIIRC) stereo Lps began to be sold in 1957. That'55 session was recorded live at a club by Tom Dowd. I can understand that he might have used more than one mike but multiple tracks in 1955?
So what's the earliest stereo recording in your collection? (The Duke Ellington 12 inch 33rpm recordings from 1932 don't count: I've never been convinced that the 2 mikes and 2 recorders were used on that session in order to make a stereo release.)