Emcom SA-4001

The "4001" is named for the postal code for Durban. A later model, the 8002, was apparently twice as good.

Serial Number 9150. The final transistor is a 2N5591 but I'm only getting about 4W out at 57.350 MHz.

There are two PCBs obviously retro-fitted (the holes for the crossbars were drilled after the sides were anodized) very professionaly, very likely factory. There is no speaker, there are four wires coming out the back and a little socket as well, maybe some models had an internal speaker but this one didn't.

The channel switch is not (and has never been) connected, there are only two crystals soldered to the PCB.

The first board is some kind of a tone encoder / decoder / selcall.

Maybe the second board is a transmit timeout / limit?

EM35A.

As mentioned before, this one is on 57.350 MHz. The left-hand crystal is for receive, it's marked 46650 which is the third overtone frequency, 46650 + 10700 = 57350. The right-hand crystal is marked 14337.5, doubling that twice gets 57350.

The Plessey SL6600 discriminates at a frequency of 100Hz, with a 10.8 MHz crystal.
I think.
The crystal filter is marked 10736, so maybe this is the IF frequency and the SL6600 runs at 64Hz?