Starting with the beginning of General Motors in 1923, chassis and platforms were shared with all brands. GMC, which historically was a truck builder, began to offer its products branded as Chevrolet, and vehicles produced by GM were built on common platforms shared with Chevrolet, Buick, Oldsmobile, and Cadillac. Exterior appearances were gradually upgraded between these vehicle brands. For 1958, GM was promoting their fiftieth year of production, and introduced anniversary models for each brand; Cadillac, Buick, Oldsmobile, Pontiac, and Chevrolet. The 1958 models shared a common appearance on the top models for each brand; Cadillac Eldorado Seville, Buick Roadmaster Riviera, Oldsmobile Starfire 98, Pontiac Bonneville Catalina, and the Chevrolet Bel-Air Impala.