I believe that below the "M" are "2 R"...Margrethe II Regina
Very simply to Liz with "EIIR"...Elizabeth II Regina
The "R" for either Rex or Regina is very much a British thing but looking at Google, Margrethe's father used an "R" as well.
It's absolutely not a British thing. It's Latin, and has been used by other monarchies long before the British began using it. The Danes have used it since their inception and their monarchy is the oldest in Europe.
