Interesting story at the US Army's Web site about the rediscovery of a historic tank. The full story is here: http://www.army.mil/-news/2009/02/25/17393-cobra-king-led-4th-armored-division-column-that-relieved-bastogne-during-battle-of-the-bulge/
And more details here: http://www.stripes.com/article.asp?section=104&article=59651
The bottom line is that a certain "Jumbo" Sherman tank from C Company, 37th Tank Battalion of the 4th Armored Division "Patton's Best" that led the way into Bastogne still exists and has been sitting as a memorial outside a base in Germany.
Here's how the tank looked in 1944
And here's how it looks recently
It appears that Avalon Hill took a little artistic license with the cover of the solitaire game Patton's Best. The tank on the game box cover has the tactical markings for the 4th Armored Division's 37th Armored Battalion, which is accurate enough, but the tank depicted appears to be a basic M4A1, tank No. 4 in the game. It's quite possible there were some M4A1s still with the 37th Armored, but the leading tank in a 1944 tank thrust was often an M4 "Jumbo" like Cobra King.
Interestingly, it appears that Cobra King was a 75mm armed M4 M4A3E2 "Jumbo" during the Battle of the Bulge. The photo above clearly shows it was armed with a 75mm, and one of the crewmen is quoted as talking about how he fired the 75mm gun "like a machine gun" during the battle. It definitely looks most like this drawing from the Patton's Best game, tank No. 12:
But the modern photo also clearly shows that Cobra King was upgunned to a 76mm gun at some point. The 75mm gun was good enough for most purposes, but was inadequate when facing first-line German tanks such as Panthers and Tigers. The 76mm-armed version of the Jumbo Sherman is card No. 13 in Patton's Best.
According to the articles there are plans to move the tank from Vilseck, Germany, where it's apparently been since the war to a museum in the US. It will also be "restored," although I'm not sure if that means it will be restored to its appearance at Bastogne or not. It appears to be in pretty good shape already, judging from the photos, so it seems reasonable to think that the tank may be restored to its Bulge appearance.
Interestingly, the fact that the Cobra King was a Jumbo Sherman explains why it's managed to survive so long. While Jumbos, as the lead tank in a column, often took heavier fire than the average tank, the thick armor let them take it. But there are lots of ways a tank can suffer an ill fate, and most of Cobra King's mates at Bastogne from C Co. of the 37th Armored Battalion, if they survived the Battle of the Bulge, were undoubtedly lost during the infamous Hammelburg Raid. C Company formed the core of Task Force Baum, which Patton dispatched on a raid to liberate the POW camp at Hammelburg where Patton's son-in-law was being held. The entire force was lost. Presumably Cobra King missed the raid because a Jumbo would slowed the column too much.
Patton's Best allows players to recreate Cobra King's drive on Bastogne. It's Dec. 26 on the Combat Calendar, A/9/H meaning Farm fields/ 90% chance of contact/ Heavy action.