Unsurprisingly it didn't work. The belts have dried up so I'm using rubber bands in the interim, and one of the wires to the play head has snapped. But with a little bit of TLC and bodging I have it up and partially running. The amount of wow and flutter is pretty astonishing and it plays a bit slow. That being said, it sounds about on par with modern cassette mechanisms, and the fact that the sound is coming out of something that really looks the part, and was probably meant for dictation, is just completely charming.
I also took a moment to make an illustration of it.
I also got some period correct(ish) music recorded from it. It's incredibly cursed.
Is You Is.mp3