This Gunn oscillator for 10 GHz was made in 1973 and was used for the first GM (Scotland) to GW (Wales) contact on 3 cm. The oscillator is tuned by a sliding short moving along the waveguide. The control is by a high precision More and Wright drum micrometer head.
The Gunn device is mounted in the waveguide under the post mounted on the guide. The output power of this oscillator was 150 mW. Between the Gunn mounting and the output flange is a series of matching screws spaced at λ/8.