I can remember when Aussie military aircraft - DHC6 and B200 were registered VH-HP_ due to being leased from Hawker pacific!
Don't recall the military ever using "VM" registrations, but I recently saw a winglet equipped King Air 350 with RAAF roundels and an "A" military registration number. I checked the RAAF web site and was amazed to find
this statement:
As a general transport, the aircraft has carried up to six passengers to destinations including Broome, Darwin, Sydney and Hobart. As a transport, the King Air 350 is flown between 25 and 35,000 feet for optimum fuel economy.
I suspect they mean "between 25,000 and 35,000 feet." Life could be very interesting - not to mention, rather busy - at 300 kts and 25 feet AGL!
