Thanks, and I am also very happy to have them in my collection.
I have the appearance that the BDM triangles to get even more rare. Unfortunately I have no BDM.
Depending on the manufacturing characteristics, I think the first denomination was "Südost Böhmen und Mähren", then late in the war it changed to "Südost Böhmen-Mähren".
Thanks to Pimpf for showing us that there were two variants of this rare triangle and thanks to Debertex for giving a very good explanation of the temporal appearance of the triangles.