Did you get it right?
One modern tracking item appears among the old library cards and stamps.

The Answer
The correct answer is: the self-adhesive barcode label.
Here is why
- The wooden drawers, index cards, date stamp, ink pad, pencils, and checkout cards fit the old library.
- The white barcode label on an old checkout card is the modern mismatch.
Why people miss it
It belongs to library tracking, so its purpose fits even though its technology does not.
What answer did you get before checking?