Does anyone know what this thing is?

[sunny6teen]

The lens is at right-angles to the ground glass. Dead Link Removed
Dead Link Removed

 

[MattKing]

This was used for transferring movies to videotape (in the day).

 

[sunny6teen]

Thanks for that ....how did it work?

 

[MattKing]

You projected a movie on to the larger, ground glass screen.
You attached a video camera to the other side via a lens adapter/attachment.
The video camera could be focused on the ground glass image, so you could record the movie on to video tape - VHS or Beta usually.

Then you could play your movies on your TV using your VCR.

Boy do I feel old now .

 

[AgX]

There is a mirror inside for changing the oriention of the image so yield a right-sided copy.