This 10 GHz detector was made by G8DPB in 1975.
The detector diode can be seen to be mounted off of the centre line of the broad face of the waveguide. This improves the match. The output is taken via the BNC connector. The three screws mounted between the post and the flange are for matching the detector to the rest of the system. It is probable that this detector worked with a Gunn Oscillator.