[Hallicrafters] Slightly O.T.: MC Jones Micro Match stuff

[John Hensley]

I have a rackmount MC Jones (AKA Microwave Devices Inc [MDI]) SWR metercalled the "Station Guardian".  Instead of the older round inline detector, it usesa small rectangular block inline unit with both a forward and a reverse feedbackline gathered into one 1/4" phono connector that plugs into the back of the SWRassembly.  This detector block uses the 1N21 type diodes.
My question are what kind of plug or connector goes into the top of the rectangularblock and are the diodes the same and simply reversed ?
The I/O of the detector is normal Type-N UHF 50 ohm fittings.  But theside or top connections have no threads.  I am guessing that a round pin andrubber grommet are what is used here but I dunno.  
Has anyone any knowledge of this?  I have been unable to find either a manual(at a price I can afford) or the details on these forward/reverse connections.  
Thanks in advance,
John W5JV