pull tabs on cans! This style of pull tab actually came all the way off and was discarded. When on a beach this became a cut foot hazard and there had to be a law to require pull tabs to remain attached to the can.
A kid could get lost in the story the viewfinder slides tell. There were no sounds but I often could picture how it was and how it would feel like going with my favorite cartoons on an adventure. The Viewmaster