They're a dead technology - printing blocks from when type, and everything else being printed, was carved in wood or metal. These are two cartoons recreated in metal and attached to wood block for printing. Unfortunately I can only read the signature on the Hal Money one which has lost its caption.
These must have been wildly common at one point, but I've only seen one other example - a Yellow Kid ad at Geppi's Entertainment Museum (which I still plan a post on. Great place).
