I initially thought of the Canberra too but, there is no tail plane incidence trim facility on this handle although, it is a possibility perhaps? The numbers are casting numbers and quality marks unfortunately.
A nice little oval plate with a Dunlop drawing number on would have been nice : )

I have a picture/drawing (somewhere), of the hand controller for the ‘Bulpup’ missile made by Dunlop, which is similar in size hence my reply in #4

I’ll keep searching!

GYD