Questions about the M-87/AIC Microphone

[QuNoobJunior]

Hello everyone!

Some time ago I bought some single visor track set for an SPH-4 online, the seller also gave to me this weird looking M-87 Microphone.

 

Front:

 

Back:

 

Back / Comparison:

 

Note that when I got the microphone, the boom mount was broken and it had no screws for the U-173/U plug. Both of these things I got from an M-138 microphone I had lying around.

By sawing the mount off the M-138 and gluing it on the M-87.

Anyway, at first I thought its the exact same as the black M-87, just made by a different company, same as the different kind of headphone elements.

But after seeing one listed on flighthelmet.com as "RARE MK-IV High Altitude Helmet M-87 Microphone" which is exactly what I have, I would like to know more about the differences and

its usage.

 

Thanks for reading!

QuNoobJunior