The U.S. state of Connecticut first required its residents to register their motor vehicles in 1903. Registrants provided their own license plates for display until 1905, when the state began to issue plates. Since then, Connecticut has used a variety of license plate designs, and has issued different designs for passenger, non-passenger, and, more recently, optional plate types that often require an additional fee. , plates are issued by the Connecticut Department of Motor Vehicles. For most classes of vehicles, plates are issued in pairs, for the front and rear of the vehicle respectively, though single rear plates were issued between 1980 and 1987. Plates were validated with metal date tabs from 1937 through 1963, then with plate stickers until 2006, and finally with windshield stickers until 2010. Plate stickers continue to be used on plates for vehicles that do not have a windshield, or are part of fleets that frequently rotate plates among vehicles. All issues (including re-issues) since 2000 are currently valid. Until 2013 Connecticut, as a rule, skipped the number 0 as the leading digit in its plates, with the exception of dealer plates. Between July 2013 and August 2015, temporary 1ABCD2 and 1AB-CD2 serial formats were used, both of which allowed 0 to be used as the leading digit. In August 2015, a permanent AB-12345 serial format was introduced, and the number 0 could be used as the first of the five digits in the serial. Passenger baseplates 1905 to 1936 1937 to 1956 1957 to present 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 in height by in width, with standardized mounting holes. The 1956 (dated 1957) issue was the first Connecticut license plate that complied with these standards. Plates continued to be validated with tabs each year through 1960. Monthly staggered registration commenced in 1961; tabs were used for expirations from May 1962 through February 1963, and stickers thereafter. The "Constitution State" slogan was first used on the 1974 blue-on-white base. This base did not hold up well and was discontinued in 1976; remaining plates were recalled in 1990 and replaced with white-on-blue plates bearing the same serials. From 1980 through 1987, only rear plates were issued as a