I have head of a custom SP they did for Spectras that involved a Real-Time clock of some sort that was implemented in place of the STATUS/MESSAGE and DEK features. The called it their ComEd mod, I believe. Somehow the STATUS or MESSAGE function would send a time-stamp or something like that, I never got a complete description of how it worked.
This does seem like it has an RTC in it, there is what looks like a cheap clock crystal and another precision crystal, or maybe that's a custom IC in the can of some sort - hard to tell from just one angle. Either way it has a very prototype-ish look to it, like there were not many made, perhaps.
Something else interesting is the long number on the bottom, that could be a unique ID or something like a silicon serial number, and that can may be an early Dallas 1-wire device or something similar.
If that custom module was Tx'ing that 5 tone on a schedule, and it came from a telco operator it would seem like that it was used as a radiophone in lieu of deploying a more sensitive AMPS or DAMPS Motorola Microtac cellular system next to the Iron Curtain. Uncle Sam was messing with Ivan right up until the KGB left Eastern Germany and East Berlin. That 5 tone could have been a primitive affiliation signal to the nearby towers, "similar" to how some of the old radios got handed off between towers.
Man I remember my first cell phone was a Motorola MicroTAC Elite that my father handed down to me. It was a beast and you could hear other people on the line if the adjoining channels were being used.... Motorola California back in the day....