erwine and estelle laverne trays ??????  

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Why would you put a television on a tray?

Haha. It's an American thing...
Haha. It's an American thing, I guess. You use them to serve food while you're watching TV. The TV doesn't go on the tray 🙂

I grew up in this country.
I even witnessed the phenomenon first hand, yet it all still seems somehow foreign to me.

The tray in that old picture...
The tray in that old picture is a TV tray -- it's a tray table with folding legs so you can put it away flat when not in use. The Laverne trays are just trays, I think, not TV trays.