This is an empty octagonal 1/4 plate thermoplastic case for a daguerreotype, ambrotype, or tintype. 

The reference number for the case is Berg1-46 and it is called "Horse Racing". It is classified as a Very Rare case with less than 60 known examples and it measures a bit under 4 x 5 inches. The tip of the bottom clasp has broken off so the case does not stay closed. There are a few minor chips along the outside edges (see listing photo 3). There is a minor crack on the top railing of the bottom half of the case (see listing photos 2 and 4). There is a gap on the side of the hinges when closed (see listing photo 5).