The house where I found the doohickey shown in the picture was almost 40 years older than me, built in 1919. My Client asked me what it was, and I haven’t a clue. Anyone? Thanks.
Hi. Russel, The way this bracket is made with two slots and a wedge shape plate, looks like it was meant to hang something like a phone, but not sure what. Bracket looks like familiar brackets of today to hang something.
Good find.
Marcel 
Deaf person lived there years ago. There was a button that onterupted the light in a room where they prob stayed, letting them know someone was at the door. There was probably a nameplate mounted as well…as long with instructions for visitors.
If that’s a little window, it provides a bit of light so visitors can find the doorbell button. No lightee, no ringee. 
John Kogel
www.allsafehome.ca
Looks like an old manual-type doorbell that has had everything but the exterior bracket removed. Is that outside?
Does look like a door bell. the top opening is for a name tag.