In 1946 Lionel also debuted its post war trains. They too featured smoking but also its ingeniously designed (also solenoid based) and realistic knuckle coupler. With the improved coupler, it also introduced its very realistic sintered metal trucks. In 1952, a few premium sets featured the A.F. version of the knuckle coupler and sintered truck. By the next year, the 'link & pin' coupler and stamped steel trucks had been discontinued. Gilbert offered conversion kits so that the new couplers could be mounted on the old trucks.