Looks like the pic was removed when Ron cleaned up the site.
Anyway the answer is:
The US T25 Medium Tank
Many people guessed this as the M26 Pershing, or a Pershing prototype. Neither is really correct although many features look the same.
The T25 was to be the first 90mm Tank gun to serve in the US Army. It was developed from the T23 (of which 250 were built) by placing a new turret, containing a 90mm AA gun, on the T23 HVSS suspension chasssis.
40 T25's were built by 1944 before a decision was made that the tank was too heavy so a switch to the T25E1 model with a different transmission and torsion bar suspension was commenced.
An further uparmoured version of the T25 called the T26 was also planned, and the same changes to that chassis as the T25 saw it redesignated as a T26E1. This tank was used as a test bed and further modifications resulted in a new model, the T26E3. 20 E3's were then produced and sent to Europe following the Ardennes offensive, and by the end of the war in Europe 310 of these tanks had reached the European theatre under the new standardisation name of M26 Pershing. Ergo the T26 (E3) not T25 was the Pershing prototype.
Congrats to the winners, and thanks to all who participated. Chris (M1abramsrules) is back from leave and will resume command of the quiz this week. Saluting you sir.