"Plastichrome" was a trade name for bright color photographs published by a Boston publishing firm actually named Colourpicture. The Plastichromes are from the 1950s and 1960s. The photos they published as postcards were frequently very much older.
Colourpicture Publishing issued these cards in vast numbers so they are somewhat easiliy come by. They had a line of novelty chihuahua poses, including this imitation of a vaudeville act.