Luria8,
Your pump is a Sta-Rite, DuraGlas or MaxiGlas.P2R____, but there are many models starting with P2R.
If you wish to replace the o-ring under the clear cover, please measure the diameter of the soft rounded groove around the top edge of the pump trap, just under where the lid screws on. That's where the o-ring sits to create the seal. The traps are either 5" or 6" in diameter for dozens of Sta-Rite pump models.
Yours appears, by the physical design of the pump trap, to be a 5" diameter.
If so, the o-ring part number is probably U9-229.
But if I were you, I would verify this with Sta-Rite, just to be sure.
If by some chance it is a 6" diameter trap, the o-ring part number is probably 16920-0012.
For more detail about your pump, can you tell by the motor, what is the horsepower, the max. load amps, the branch fuse rating amps? Is it a Single speed, Two speed or a Three phase motor?
All this info can help identify your pump for future reference.
I have a similar but not identical pump, and I'm looking at my owner's manual in order to assist you. That's why I can't absolutely guarantee the part numbers for your particular pump, not knowing the model nor the age of it.
Best wishes,
Alan