need model number

I am a newbie here. Hopefully you gentlemen can help me. I recently acquired a yardman riding mower with a 50" deck. Unfortunately the model number is missing, MTD tells me there is no way to find out the model number without the plate.

it has a Kohler 20hp engine
Model # MV 20 S
Dis LC 570
Serial 2503702686

I do not know if it is possible to determine the year or model from this info but, hopefully someone here will be able to help.
thanks in advance