They are studs....meant to be used on a shirt with 2 button holes.....common on a man's formal shirt....but also sometimes seen on women's blouses.

Can be used as cuff links on french cuffs.

No they can't....
Cufflinks have more space for the layers of fabric involved in a French cuff shirt

Here is a link that might be useful: Men's formal set.

Umm....I knew that.....just kidding. I have never seen such a contraption before, but sure makes it easy to find when you know what they are! Thanks :)

Removable buttons for a woman's blouse, because dry cleaners RUIN buttons or steal the expensive ones, or so you can move buttons between blouses.

My fashionista aunt had several sets. They slide through a hole in the under layer, and button normally though a buttonhole.

They look more like buttons for a woman's blouse as lazy said. It is unlikely that a man would have had flower studs-at least none that have come down through our family and we have some from the late 1800s. I think they would be fun to have!