Odd you found them with numbers or writing.
First guess is tree or utility tags. No wear around holes. Definitely nailed to something stationary.
Good luck. Nothing more aggravating then finding a tag with no writing.
Nobody I know has ever found what those are, many shapes and decorations are found but never id,ed.
Probably used on something leather
They have been found with another part to them.
Saddle strap guides
Alot of people have said that , but not a single picture of any saddle, harness or bridle shows them.
I have searched for many hours over many years for the strap guide idea and furniture hardware idea ,as have others.
Hope someone can figure it out.