I bought a used MTD Yard Machine 16/42 riding mower. The ID plate under the seat is illegible. Is there another way to identify the model? I need to replace the drive belt but there are several versions at Lowe's and I don't want to swap it out via trial and error.

Hi
I have recently replaced the cutter drive belt on my MTd. I was told that the belt number will be on the old belt.

Well, the plates are usually illegible for one of two reasons, the first being the unit was sold directly to an employee at a mtd plant, and the other the unit is stolen. Perhaps though, it could be some other reason.
Did you purchase / obtain the unit from a trusted person?
And the only other way to tell is by mere comparison.