Info in mil. receiver needed
 

I'm not sure if this is the right place, so please advise if I should be
posting this elsewhere. I'm into restoring vintage commercial radios,
Philco, Zenith, etc., and a friend asked me to try to find some info on an
ancient military receiver for him. All he can find on the name plate is
RME6900 Receiver. I am assuming this is a code number refering to the unit
type and manufacturer. Anybody out there with knowledge of this receiver?
Where can I go for more info? Thanks in advance.

Tom