Thanks for the clarification Rob. My evidently unsophisticated operating premise has been:
the
M100 is a Canadian 1/4 ton trailer from the 1950s, recognizable by its rounded fenders and contemporary to the M38, M38A1 and M151;
the
M101 is another Canadian made 3/4 ton (or similar capacity) trailer from the 1980s and onward, recognizable by its high "truck" stance and heavily reinforced box; and
the
M416 is a 1/4 ton trailer for the Iltis, surplussed in the last few years and distinctive by its angular fenders and warning triangles on the rear panel.
This discussion is ruining my reputation for never making mistakes. I now have to suffer the indignity of admitting to a second mistake in my life. (Oh, the shame of it all .... )