Looks like the typesetters at Alco Research & Engineering (which printed labels, and handled the metal plating [ and thus the delta numbers ] for Monarch) didn't bother to change the cat. # when typesetting the stereo labels. Look at an RCA pressing, more than likely on the stereo copies the SLP prefix would've been on the labels.
Incidentally, the matrix #'s on the mono issue would've been SR4M 3424 / 3425.
Slightly confusing on this one. Label shows catalog as LLP 2033, but clearly also shows it is Stereo. The front of album jacket has large STEREO across the top and shows catalog as SLP 2033, which would be correct for the stereo release. I will upload album cover later. Also interesting to note that House Of The Rising Sun is credited to Rod Argent and Suzie Q is titled Susy Q on the back of the jacket.