The Mic is stamped JM47. It has a BNC cable connector on the bottom which feeds into its own power supply box 5.5 inch by 4.5 inch by 2.5 inch.
The box is in your green livery and is marked as JM47 Tube Capacitor Microphone. The front just has an on/off rocker switch.
The rear has normal kettle lead socket for power, the BNC socket to connect the cable and a standard XLR socket as output. It says made in England by Fletcher ElectroAcoustics Torquay giving a Newton Abbot Tel No. (Quay House I expect)
I would send a photo but can,t seem to crack that. Does that help Identify it?