I am not sure if the "ROYAL M" brand evolved over time, starting with German production and later moving to Japan. Alternatively, the two lines could be completely unrelated, with the name match being pure coincidence. Known German series include Bridal Rose, Mignon, Oriental Spring and Summer Evening; the Japanese series include Charlotte, Platinum Knight, Tiara and Twilight Rose. There are probably many more series out there.

M150901a
Framed "ROYAL M" above "BAVARIA - GERMANY" (series "ORIENTAL SPRING").

M150901b
Crowned "ROYAL M" above "BY MITA SHOTEN" and "JAPAN" (series "PLATINUM KNIGHT").

M150901c
Crowned "ROYAL M" above "BY MITA" and "JAPAN" (series "SWEETHEART").

M150901d
Crowned "ROYAL M" above "BY MEITO" and "JAPAN" (series "TIARA").

M150901e
Crowned "ROYAL M" above "BY MEITO" and "JAPAN" (series "CHARLOTTE").