The Fisher Trainer

I am trying to track down more details of what was known as ‘The Fisher Trainer’, a ground gunnery training device for air-to-air gunnery (I think fighters) invented by former 111 Sqn Battle of Britain pilot, Sqn Ldr A G A Fisher (later Sir Anthony Fisher).

The family have been family friends of mine for years, and they do have certain details – including an original operating handbook.

But….does anybody know what one of these looked like? Where were they used? And do photographs exist? Were they known as something completely different in service?

Any help would be very welcome.