The Gramdeck was invented by a Mr Tutchings for the Royal Radar Establishment (a firm who produced electronic components for UK defence contracts used in Warships and Planes).
To use the reel to reel the metal plate slips over the turntable and spindle of your record player. As your deck turns it rotates a rubber belt connected to the take-up spool of the Gramdeck. Along with the plate, the set also included a plastic table microphone and a tiny amplifier that ran off a 12v battery. The mini amp was supposed to be able to run for 600 hours off that one battery. The mechanism really was as paired back as possible, and although you could play and record on it, your Gramdeck would neither rewind nor fast forward meaning you had only one shot while recording.