bbrowniii:
I believe (and someone might clarify this) that the M4 was the variant that landed on D-Day with M4A1 and M4A3 variants arriving in late July of 44.
M4s and M4A1s were the main versions used in Normandy. Some late model M4A1 (75mm) with the angled hatches, and M4A1 (76mm) also were there. The M4A3 (75mm Wet) did not start getting in to battle until late 1944 after the Normandy breakout.
But your work looks great and the diorama idea is excellent!