The early 71-123 Cub Cadets had the S/N stamped into the forward, raised , square, boss on the right side of the transmission case. The numbers are about 1/8-3/16" high in a horizontial line. Later 71-123 (and later models) had the S/N on a metal tag afixed to the rear of the transaxle (may be behind a rear frame opening cover on some), and later models went to a tag on the left side of the frame by you left foot. While I'm at it, the Original models had the # stamped into the gear reduction housing, on the right side, just forward and above the square pipe plug, in a vertical line. The 70/100 # was on the gear reduction housing, right side, vertical line on the early ones, and on the square boss on later ones like the early 71-123. The S/N's were STAMPED into the the surface. Any number that is a raised part of the casting is a part numher. The exception is the S/N's numbers on the metal tags, they are a raised or embossed number.
