Simple holder for pegboard. Fits into the bigger “keyhole” like the hole of some pegboards.
I was searching for the Internet, but almost all holders for pegboards are designed for the small holes and not for the “keyhole” like which I have on my pegboard from the Czech company Mars Svratka https://mars-svratka.cz/produkt/nastenny-panel-30.
The author marked this model as their own original creation.