Has anyone heard of the brand Operadio?

Yes . You can find schematics herehttp://www.nostalgiaair.org

Here some infohttp://www.radiomuseum.org/dsp_detail.cfm?company_id=3000

some reason did not post link right

http://www.radiomuseum.org/dsp_hersteller_detail.cfm?company_id=3000

Thanks for the links. Here is a photo. Some sort of old slide projector with a turntable. I think Operadio made just the phono amp.

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-Phono-Filmstrip-Projector-Operadio-Dairy-/320531065849?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=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

They also used filmstrip projectors in schools, along with a record played on any player they already had. As noted, at the tone you advanced to the next frame. The filmstrips were coils of 35mm B&W film, no reel required. You fed the coil in the top, I think, and it recoiled itself as it emerged frame by frame at the bottom.