Well it says right on it what you've got...an Explainette! I have one somewhere, they were for traveling salesmen to make presentations in the days before Powerpoint (or computers, for that matter...). The cover for the unit has a small projection screen inside, or you could use a blank wall. I don't have any filmstrips or records for mine (they came as a set, when the soundtrack played a short tone, you advanced to the next image on the filmstrip). Here is one on eBay with a filmstrip, but no records:
http://cgi.ebay.com/Explainette-Phon...item4aa123ebf9
Operadio had been around since at least the 30's, they made audio components (speakers, amplifiers) on contract for lots of different manufacturers. I have a jukebox from 1933 that has Operadio speakers.
--Bob