On second look, I noticed that the letters are not perfectly aligned to a common baseline: in “MENX”, M and especially X sit a tad higher than E and N. This suggests they were applied individually – which can mean dry transfer lettering*, or some cut-and-paste technique.
*) It’s not Letraset. The next best thing that they carried at the time were the extrabold weights of Raleigh and Romic.