On top of which, that doesn't look like a card catalog. Rather, if it is then why are there three different card sizes when there are only two major types of card catalog sizes? See http://collections.infocollections.org/ukedu/en/d/Jg28doe/13... .

(Only one of those boxes looks like it might be the right size.)

Plus, the card catalogs I've used have a rod that goes through a hole in the bottom of the card. This helps keeps the cards from falling down, or falling out should someone drop the drawer. The rod is usually visible on the front of the drawer.