Yes, it's that old favourite, the Viewmaster*. I loved this when I was a kid. It was like a slideshow but all 3D and right there up against your eyes with people pointing towards and poking sharp things at you! We had two of them, naturally, so that the Brother and I wouldn't fight over it. We found a way around this, equally naturally, by fighting about who was looking at what reel.
We had a good selection and they're all still there in the little box, somehow surviving being punted around in various rounds of decorating. It's representative of the tastes and should come as no real surprise. The Muppets? Check (both the regular and The Muppet Movie reels). Doctor Who? Oh yes (Tom Baker in Full Circle for those of you who are curious). Transformers? As if you really have to ask. Spider-Man? Doing whatever a spider can, right there. All a little worn from plenty of enthusiastic Viewmastering but still in perfectly usable condition.
The real surprise, though? They still make them! I honestly thought this had died out in the 80s. I may have to get me to a toy shop...
* The red one we had seems to have disappeared, though - the remaining one is purple.