[Milsurplus] Mystery FSK/DFSK demodulator CV-2310/G

[Nick England]

Howdy men. I received a mystery item photo today - CV-2310/G FSK/DFSK
demodulator
Photos at http://www.navy-radio.com/puzzlers.htm#cv2310
I suspect it may be an NSA signals intercept gadget given the ID tag,
odd shift freqs, and DFSK (did the US military ever use DFSK?)
Any info greatly appreciated.
Cheers,
Nick K4NYW
www.navy-radio.com