Original Stentorphone soundbox.

Between 1910 and 1917, Harry Alfred Gaydon (1878-1944) created and managed a company for the manufacture of his own inventions, includ9ing this air-operated megaphone. In 1917, Gaydon joined the staff of Creed and Co., carrying out experimental work on aircraft acoustic apparatus. Gaydon appears to have worked in Croydon in engineering firms for most of his career.