Holy crap victor what he heck is that thing ???
It is a Radio Service Monitor, and is used for setting up and repairing radio equipment. IOW, If you were setting up transceivers on a particular frequency you would use the IFR to optomise the deviation and sensitivity.
It is also a lab quality spectrum analyzer. So it is perfect for tracking down those elusive frequencies, or sources of RFI. In fact, these are used by the RCMP and other surveillance countermeasures groups.
Some have plug in modules for use in intercepting cellular phones. Not that it makes any difference now, but they were also one of the only receivers allowed to be cellular receive capable; exempt from the US laws restricting cellular coverage.
The best thing is that it will transmit and receive from "DC to light" with lab quality accuracy.
Victor