STC Transcription or Recording Gramophone pickup Circa 1935 38

Highly Unusual Gramophone pickup made as either part of a Production prototype batch that never made it to actual production or a Studio recording head made by the Standard Telephones & Cables Company of England around 1935-38 & bearing the STC logo on the lifting arm.
Cast Aluminium tonearm with what looks like a hand machined pickup of the moving Iron or Variable Reluctance type, reminiscent of the HMV Hyper Sensitive type from this latter part of the 1930's. This is what Iv'e based my date estimate of this pickup on. This pickup came with 3 others of the same type & all 4 have hand written part numbers on various areas. these pickups measure around 11 Inches from the rear pivot to the actual Stylus point which is a glued-in Diamond or sapphire & still in good, playable condition. There were recording set-ups in the 1930's that used 4 pickups to make direct recordings to transcription sized wax discs & perhaps this is what these were built for. In any case I can find no concrete information on these .
A really nice tonal output from this pickup that needs to sit lower than normal to obtain the correct needle angle to play a record as the needle sits at 90 degrees to the tonearm......which is another reason I think these were built for recording.