That isn't a typical Rheem model number, are you sure that isn't the serial? If it is the model number it is a 2.5 ton :)
The model # indicates unit characteristics including capacity not the serial#. The serial # generally tells where , when , by whom and what components were used when it was made.
2.5 tons
1.5TON.
3.5 Tons
3.5
4 Ton
7.5 tons.
4 ton
3 ton
2.5
hvac unit