I assume you realize that the plates in your photos are not genuine Cat data plates.? That being the case can you trust any of the information that is on them.?
Shouldn't there be S/N's stamped in the frame some place? Thinking they used to be at the left rear near the top, at least seem to recall that on the D6C's.
Serial Number should be stamped on the LH upper rear corner of the bevel gear case. There ought to be a S/N plate in that same location as well. Sometimes if the tractor is equipped with a ripper the ripper frame obscures the plate/stamped numbers.