Hi Thomas,
On you photo in post #3, both Bavarians are wearing standard Minenwerfer unit straps from that period. The one on the left is also an M, not and H. The Ws are out of view. The Bavarians wore the unit number above the MW, rather than below it, as will all other contingents. This pattern shoulder strap was worn primarily on the simplified (vereinfachte) tunics and is sometimes referred to as the M07/15 or in Europe, as the M14, based on the year of the first simplifications of the M1907 tunic.