The Campagnolo gear-shifting system introduced in 1951 was called Gran Sport.
Gran Sport was developed by Italian engineer and cyclist Tullio Campagnolo, whose company had begun producing bicycle components in Vicenza in 1933. The design was a parallelogram rear derailleur, a major step beyond earlier mechanisms because it moved the chain across the sprockets more efficiently and made shifting practical without removing the rear wheel.
Historical references distinguish between early Gran Sport versions. Campagnolo presented a twin-cable parallelogram derailleur in 1949, while the 1951 version is commonly associated with the single-cable Gran Sport system. That difference explains why sources may mention both years without referring to entirely different product families.
Gran Sport should not be confused with Record or Super Record. Those names became associated with later, higher-level Campagnolo component groups. The Gran Sport name belongs to the pioneering derailleur system that helped establish Campagnolo as a leading road-cycling component maker.