Sticker on the pump body (the part with the basket), not on the motor. Motor labels from Century, A.O. Smith or Regal won't match parts.

Label on the side of the tank near the base. Size is in sq ft, e.g. 420 sq ft = C4030 or CCP420.

Rating plate inside the front access panel. Note the BTU and gas type (NG or LP).

Molded into the body or printed on top. Robotic cleaners: on the power supply.