That is a beauty. Clever design, to be able to pour off accumulated oil by means of the spout. It's used on a cookstove over the firebox, by removing two covers and the "I" piece between them. The unit sits down inside the top of the firebox over a bed of coals and the draft of the stove theoretically draws the smoke from burning fat down into the box and up the stovepipe.
So, where was this Griswold convention?