Photograph of Frank Muller and man with gold bond, Southern California, 1931. "Pennzoil, No. 28490, Guarantee, We guarantee Pennzoil motor oil to last longer, lubricate better, cost less per mile. Drain and refill the crankcase of your car with the correct new, perfected S.A.E. grade of Pennzoil. Test this oil for 1,000 miles or more, maintaining the oil level, prior to February 1, 1932. If it does not give you entire satisfaction its cost will be refunded to you upon receipt of this card properly filled out. The Pennzoil Company, 155 West Washington Street, Los Angeles, California., Make of Car, Mileage, Grade, No. of quarts used, Date, Owner's Signature, Dealer's Signature, Street, City" -- on certificate. "[ilg] Cal [ilg]" -- on license plate.