Instrument id

Hi all , i have resently aquired a few prewar civilian instruments as my knowlege dosent cover this area can anyone here help

Turn/slip indicator made by H. Hughes & Son Ltd , no markings on case.

RPM MK 16 made by S S & S Ltd London

Airspeed 40 t0 240 MPH made by S S & SLtd no other markings.

Turn/slip and airspeed appear to be NOS . Can anyone shed some light on what they would be fitted to.

cheers dave