Does anybody know the manufacturer of the horn in the "Let's Face it" film between the guy turning his head and the model "A" here is the link http://www.youtube.com/watch?v=yXxqRUUPgDQ
I'm not too sure either, but I'm quite certain that it isn't a Diaphone. Gamewell Diaphones are air-driven piston horns, not diaphragm horns like that one.