The tiniest and most charming of all pins!  I have just about the same pin in my collection and it is so perfect for many outfits!  These are rare.

This is an enameled pin set in brass.  There is a plain pin clasp back. 

3/4" long by about 3/8" tall

Please know that this is an old jewelery item at least vintage, but maybe antique.  You will see a slight age patina on the back.  This pin is in excellent working condition.

Modeling is a 58" or SD sized Kay Wiggs Nelly doll.  This is a photo to help you reference the size.