Is this something you have actually seen, or just a photo you've found?

Haven't seen anything quite like this. It's going to be 1) a microphone 2) a speaker or 3) a separately- mounted variable condenser for tuning. More photos from different angles might reveal whether it has the large diaphragm of a speaker, the small diaphragm of a microphone,and if those streaks radiating from the center of the device are names of cities and countries, the dial of a tuner.

I have a feeling it's a microphone, suspended in an isolation cage as they often were: like the one Neville Chamberlain is using here.