RadioBanter - Mystery National Receiver NC-127D

I have an interesting old National receiver with no documentation,
labeled model number NC-127D. It appear very similar to the NC-101XA,
but it's painted battleship gray and has a rack mount front panel with
handles. There are more control knobs on the front panel than the
-101XA, and the S-meter is located at the upper left corner of the front
panel, rather than behind the near left side of the tuning dial
escutcheon as in the -101XA. It tunes from 540 kHz to 30 MHz. The
knobs are an off white color.

A tag on the front says "Order number 2507" and gives a manufacturing
date of 6-1-45. I have it from the former owner that the "D" stands for
diversity, and that it was designed to be part of a diversity reception
system employing at least one other receiver like it. There is a coax
connection on the back for import/export of the local oscillator signal,
but unfortunately I have only one radio.

Does anyone out there know anything about this radio?

Bob
WB4TGG