L2650 serial number locations?

Buying parts but not sure of my serial number. Parts are based on a two ranges of serial numbers. My tag was once visible over the left front axle but over 30 years (bought in 95) is no longer readable and it was never written in the manual. Dealership no longer has a record of the original sale. I’m the original owner so it isn’t a stolen tractor.

Does anyone know of an alternate location, like stamped into the frame, where I might find this? I checked under the seat as well. It also has the original engine so I can probably locate an engine serial number stamped in but not sure how/where I would cross reference it.

Thanks!