This Marconi one valve receiver was made by
The Marconi Scientific Instrument Co.
of St. Anne’s Court, Dean St. Soho, London in c1922.
It uses an old type’Q’ valve invented by Capt. Round in 1915.
This was the first valve to reduce capacity between
the grid and anode of a triode valve by bringing out the connections directly on the glass envelope. This receiver would have been illegal to use after the end of 1922 as, using reaction in a one valve receiver was not allowed by the GPO due to radiation from the aerial when excessive reaction was being used. The BBC eventually issued a booklet about this...
....see “Don’t Oscillate,” in main wireless menu.
There is an intriguing technical puzzle about this receiver