These rather unappreciated intercoms were made from the early 1920s until the late 1950s. Dictograph sold worldwide, and their phones must have been quite well built, judging by the number that have survived.
My first example is from Britain in the late 1950s approximately, with a walnut-veneered cabinet that is still in surprisingly good condition for its age.
The second one, in what appears to be stained beech or pine, is probably one of the earliest U.S. models from before World War 1, judging by the separate transmitter (behind the elaborate Dictograph badge) and receiver. This is a typical intercom from that period, although better finished than most.
The third example is a British model from just before World War 2, from the handset design.
The dates are only guesses based on the handset styles - Dictograph did not seem to believe in dating their products. I am looking for information on this company, and I have written a short history of Dictograph and its phones. Can anyone help?