I didn't see that someone else told you already sorry :) I have odd clips and a couple sets from my husband's aunt who was a show girl back in the 1910's to 1920's so these are pretty old. It is too bad you don't have both of them <3
These were not originally shoe clips! the style of dresses in the 30's allowed for fold back collars and these were called collar or dress clips. They came in pairs.