This just of academic interest as the question has been settled (i.e., for many years "M" and "S" denoted the trigger fitted)!

But HW has changed around many designations over the years, seemingly with a desire to confuse future collectors, LOL. This page is from a 1959 Weihrauch brochure - at that time the HW 35 and HW 55 had the Rekord trigger...but NONE of the four versions of the HW 50 did.