Vintage Corner Brackets/Border Corners with Glass Screws - set of 4

Glass screws have a flower or star shape

Vintage/maybe antique; unsure of exact use for these; found in a drawer during estate cleanout.

Potentially for holding a mirror or picture frame?

Mounting edges?

Photo corners?

Book corners?

Corner protectors?

Each metal bracket measures 7/8" with the indented area measuring 9/16" long x 1/16" deep to a very small lip and 1/8" total indented depth

Each glass screw measures 3/8" in diameter and 7/16" in exposed screw length

Each nut measures 1/4"

Vintage/maybe antique; metal has rust and tarnish