I did some research with 2 AIs
This silver metal part is the stud or key for a quarter-turn panel fastener.
These are also commonly known as:
- Turn lock fasteners
- Cam lock fasteners
- Dzus fasteners
What they're from:
Originally designed for hanging pictures, mirrors, cabinets, or other wall-mounted items
Common hardware found at any hardware store
What they do:
- The round hole at the top accepts a screw head or nail head mounted on a wall
- The narrow slot below allows the item to slide down and lock into place
- This creates a secure, flush mount against the wall