This (most likely doctored) photo of a picturephone in 1939 or 1940 is featured in the book Exit to Tomorrow: World's Fair Architecture, Design, Fashion 1933-2005.
The weird thing is that I haven't been able to verify the authenticity of this photo outside of this book. In fact, it is rare to find mention of a working picturephone, with any degree of specificity, pre-1955. Anyone who might be able to shine a light on this is encouraged to educate us all. The caption to the photo appears below.
Charles F. Kettering, General Motors vice president in charge of research, appeared on the screen in the first demonstration of what might be termed the "television-telephone." By means of this equipment, which was the first of its kind ever operated in this country, Ernest L. Foss could see the person to whom he was talking. The apparatus was displayed at the formal opening of the Previews of Progress, General Motors Research's stage show at the fair.
Tomorrow's TV-Phone (1956)
Television Phone Unveiled (1955)
Futuristic Phone Booth (1958)
Governor Knight and the Videophone (Oakland Tribune, 1955)
Face-to-Face Telephones on the Way (New York Times, 1968)
Picturephone as the perpetual technology of the future
The Future is Now (1955)
Discovering the Videophone (1970)
A Ballad for the Fair (1964)