I spoke to my daughter. She said the device was mounted on the wall with the "speaker" area on the top, so I "guessed" right on that.
She said that there was an intercom system in the house and in the same room was a control panel with a speaker and a microphone. So it seems unlikely that there was a second intercom speaker in the same room, but who knows. She also did not know if the wires from the item in the picture went to where the intercom control panel was. Next time I see her, I'll look and see if it is a speaker in the tin housing, but I agree it looks like one. If it was a Ma Bell device, would it have a speaker or a bell?
The flanged opening on the bottom is also interesting as to what it was for.
The whole idea that the purpose of this box is no longer readily known after only 50 years or so is fascinating. In its day, I'm sure it was common place. Now, not so much. Some other technology leapfrogged it.