It is strange to see bookends featuring a cowboy positioned in a Greek revival archway, but here they are. The cowboy is mounted on a rearing steed. The archway is constructed with typical Greek Ionic columns and with a keystone.
Today we do not associate cowboys with ancient Greece, but western movies were already popular in the USA in the first decade of the last century, and Victorian art styles were still popular as well. Greek revival was a Victorian style, so the bookend artist probably saw no conflict with cowboys in Greek archways. The image, though, suggests that the bookends were issued very early in the twentieth century to please both the Victorians and the lovers of Western action. For example in 1903 the western film THE GREAT TRAIN ROBBERY showed the outlaws escaping on horses.