The M46 was an interim version of medium tank made prior to the proposed acceptance of a tank called T42. The tank was basically an M26A1 Pershing with a new Continental 12-cylinder air-cooled engine producing around 800 HP in place of the much less powerful 8-cylinder water cooled Ford GAF in the Pershing. From the front both tanks are nearly identical, but the M46 has a squared-off back end with twin mufflers on the fenders.
T42 never saw the light of day, but its turret was combined with a reworked M46 to produce the M47 Patton II. All of these tanks were eventually replaced by the M48 series in the mid 1950s.
Only a handful were lost in action, most notably four stuck on a train during the December 1950 withdrawal that had to be destroyed by the USAF.