Eric,

Have not seen one this old in over twenty years. Suspect this is a 60's model. I believe that is a L51 model. The tire is actually pneumatic, this could be air filled or solid rubber. The serial number should have two letters, starting with AB for 1960 up to AK for 1968. 69 to 72 had block serial numbers. You can still get parts for the lift from aftermarket warehouses. Good Luck