Between April 1952 and December 1954, nearly 7,000 M48s and M48A1s were produced, with production contracts for an additional 2,500 tanks to be built through 1956. Army units in Europe immediately received 2,120 of these early M48A1 tanks, but correction of ARCOVE defects discovered after production delayed the fielding of the remaining tanks. The Marines Corps however continued to use the M47 Patton. The M48A1's width proved too wide for many European tunnels, complicating rail transport. Operational readiness rates of M48-equipped units tended to be low. The tanks continued experiencing engine, transmission, track, and suspension problems, and the M12 stereoscopic rangefinder was uncomfortable to operate. However, the M48A1 was considered an even match for its Soviet counterpart, the T-54 and fielded to combat units in Europe. On 25 October 1954, the Army decided to amend its designation of the M48 tank. Thereafter, the tanks with the original Mod A hull design and the Chrysler-designed M1 remote-control machine gun mount attached to the tank commander's pop-up hatch would remain the 90mm gun tank M48. However, all those tanks with the Mod B hull (some production M48A1 tanks had the Mod B turret) and fitted with the new small turreted M1 cupola armed with a .50 caliber M2HB machine gun would be designated as the 90mm gun tank M48A1. M48A1 tanks with 5 return rollers and the ModB driver's hatch were modified to the M48A2 hull configuration. The hull's armor framing for the engine compartment was modified. In addition detachable headlights, armored boxes around the taillights, newly redesigned mudguards, an updated fuel delivery system and a tank infantry phone were added.