Trade cards are a “single piece of medium weight paper slightly smaller than a post card, printed with decorative images which directly or indirectly promote a commercial product, service, or event. Trade cards were used widely from the 1870s to the end of the 1890s, and were commonly distributed to the public at store counters, expositions, and through the mail.” The Daniel K.E. Ching Collection of the Chinese Historical Society of America has over four hundred trade cards produced in the United States and Europe that contain racist depictions of Chinese and Chinese Americans. Several images have been posted online. For a bit of context read the essay.
Found via American Samizdat.