"M" = Magadan , Sea of Okhotsk, Far East
"F" = Vladisvostok, Far East, Sea of Japan
"D" = Sevastapol, Ukraine, Black Sea.
Here in Australia the most regular is Magadan and Astrakhan ("A") in the summer "F" is most common.
Yes, "D" Sevastapol is a regular here too on 10MHz just after Grey Line in our evenings.
I wonder if they all run the same transmitter power? One of the more elusive ones is "V" Khiva, Xorazm region of Uzbekistan.