The AMC 650cc twins were first introduced in the 1958 model year but are descended from the 500cc twins first produced in 1949. Enlarged to 550cc (all for North America) in 1954, they became 600cc models in 1956. The 650cc models were available as road models (G12 & G12DL), "dual sport" models (G12CS) and the sport road version pictured here, the G12CSR. Other than tires and engine sprockets, the G12CS & G12CSR were pretty much identical with their quick disconnect lights, alloy fenders, small sporty gas tank and magneto ignition. The AJS equivalents models were: model 31, 31DL, 31CS and 31CSR. The 1961 G12CSR pictured here is all original except for the small handlebar windscreen.