From what I can gather, military radios use dynamic microphones (low impedance, Bose spec 5 ohms), and civilian use electret (higher impedance 220 ohms to 2200 ohms, Bose again, and of course electrets need a bias voltage supplied from the radio).
So, you'll need high impedance.
Info gleaned from Bose and David Clark websites.
Hope this helps,
RR