Lustraphone desk mic or speaker?

Here's a funny little thing from Lustraphone, found on ebay…..

This was sold as a desk microphone, but it may actually be a small speaker. Or both! It looks very stylish, with tolex covering and brushed nickel finish.

The 'device' measures 600 ohms at 1KHz, and 50 ohms at 100 Hz. Inside, the dynamic element looks more like a small speaker than a mic element, although of course the two things are fundamentally the same technology. When wired as a mic it is pretty lo-fi with a narrow bandwidth. And it does transmit as a speaker too. My guess is that it was part of an intercom system and serves both purposes.

Whatever the intended purpose, one can easily imagine this on a gentleman's desk, so that he could talk to his secretary whilst smoking a pipe and considering important, worldly matters… like this chap!