[2] Since reciprocity for license plates between the Canal Zone and Panama did not exist until 1950, old photos often show local vehicles with two different license plates mounted on the vehicle.

[3] In 1956, the United States, Canada and Mexico came to an agreement with the American Association of Motor Vehicle Administrators, the Automobile Manufacturers Association and the National Safety Council that standardized the size for license plates for vehicles (except those for motorcycles) at 6 inches (15 cm) in height by 12 inches (30 cm) in width, with standardized mounting holes.

Included in one of the sets issued by General Mills was a Canal Zone license plate.

Other plates in this set included the following locations: Alaska, District of Columbia, Dominican Republic, Guam, Hawaii, Italy-Military, Philippines, Virgin Islands, and the Maharajah plate with a golden double headed eagle.

[6] Note that all of the license plates issued for each state, province, territory, or country had the same serial number (Canal Zone plates all have the W3966 serial number).