Good information all around here.

I hadn't properly considered Lehane's point earlier. These CPM20/CPM46 may be generally user-unrepairable for internals, unlike some older, larger gear with greater documentation and a larger market share. This is often the case for most test equipment produced after the mid 1990's at latest, in general terms.

The failed battery is to be expected. I'd be surprised if another jobber battery couldn't be levered,  or soldered in there.

This counter is a little insensitive, starting to read at -20dBm in some ranges. It seems this instrument may be ideal in a field test setting however, something like testing a rover link whilst on hilltop. Perhaps fit for purpose for that. Given the current surplus status of these units, good ones may be available cheaply now if anyone is interested further.

With the obsolescence of TDM point to point Microwave, I don't expect a resurgence of this kind of gear in future elsewhere. Perhaps?