On Saturday I tested the PRC-320 on 20m with the 2.4m whip and the mic element outside of the handset's case. It is a noise cancelling mic that is used in the boom microphones of the Clansman headset, and I do not think it fits inside the handset, because the latter is not open on the back to allow the noise cancelling feature to work properly. I will have to find out more about this.
I made a short QSO with IY7NGM/P, a special event callsign to celebrate Marconi's Nobel Prize in Phisics one hundred years ago.
This is a video of IY7NGM/P last summer featuring a QSO with YO9APK.