Great clip! It reminds me that I want to get the DVD set.
I agree with Tex and Louis, it's a Priest. It was a development of the Sherman chassis, with the upper hull modified into an open fighting compartment, with a howitzer installed. It took its name from the machine gun position mounted at the right front of the compartment. Some thought it looked like the pulpit in many churches.
Newkirk's helmet is a cut-down Pickelhaube, too. After the First World War, old Pickelhauben were recycled as crash helmets, and as fire fighters' helmets. The spike and its mounting base were removed and replaced with a ridge spine that ran fore and aft, the cockades were removed from the chin strap mounts, and, for fire fighters, at least, a stamped metal shield in the coat of arms of the home municipality was mounted on the front.
Prost!
Brad