So for the XM177E1, I've seen the DOD acceptance stamp on the right side of the mag well. On the XM177E2, I've seen it on the front of the mag well. Is this correct? Is there a time frame when they went from the larger stamp on the side of mag well to the smaller stamp on front? Was this not consistent in the position of the stamp?

What about the M16A1 in the 1969-1972 period....were there acceptance stamps on these and where? When did this practice end?