Marconi Scientific Instrument Co
of 40 Dean Street, London
1922 Advertised as maker of inexpensive home receivers using Marconi's patents[1]
1922 Change in timing of weekly broadcast of concert programme from Writtle, Essex[2]
1924 The Marconi stand at the Palace of Engineering represented Marconi's Wireless Telegraph Co, Marconi International Marine Communication Co, Marconiphone Co, Marconi Scientific Instrument Co[3]
After this the activities of the company were probably absorbed by the Marconiphone Co[4]