Did you get it right?
Two modern food-service details slipped into this 1950s theater concession stand.

The Answer
The correct answer is: the tamper-evident bottle-cap ring and calorie number on the menu.
Here is why
- A soda bottle has a plastic tamper-evident ring beneath its cap.
- A calorie number appears beside a drink on the menu board.
Why people miss it
Both clues fit a concession stand, but those packaging and menu rules arrived much later.
What answer did you get before checking?