 Complete the following phrase:  Cooper built up to 300 single-and twin-cylinder cars during the 1940s and 1950s, and dominated the F3 category, winning 64 of 78 major races between 1951 and 1954. This volume of construction was unique and enabled the company to grow into the senior categories; With a modified Cooper 500 chassis, a T12 model, Cooper had its first taste of top-tier racing when Harry Schell qualified for the 