The diagram (above) is from one of the patents, and may be the first tube ribbon mic!
Harry Olson, Marconi, July 1932.
Improved ribbon mic with tube amp and better housing. Possibly the first tube ribbon mic!
Olson, Marconi, May 1933.
Directional microphone with velocity and pressure components connected in series.
Otto Kolb, September 1933.
Ribbon mic with 1 to 1.5 micron ribbon and holes in the pole pieces for improved air way.
Andrew Swickard, Bell Telephone Labs. July 1936.
Ribbon microphone with both velocity & pressure sections
Thomas Julian, GEC, March 1944.
Improvements in ribbon microphones.
Horace Duffell, Radio Gramaphone Development, June 1947
Adustable magnet pole pieces.
William Cragg, Standard Electric Corp. December 1945.
Velocity microphone with ribbon supported along its edges
Helmuth Eckardt, Bell Telephone Labs, May 1949.
Describes a 3-zone ribbon to eliminate distortion and improve frequency response.
Donovan Shorter & Hugh Harwood, BBC, March 1953
Improved ribbon microphone design. Looks very much like the STC / Coles 4038!