This is a rare and mysterious issue I wish I knew more about. They are very similar to Exhibit cards with postcard backs, except there is no indication of the manufacturer. Each one is the only example I've ever seen, and they were all obtained together. It features three Cuban players, all of whom played in the Major Leagues. Includes Jose "Acostica" Acosta, Emilio Palmero, and Pedro Dibut. Dibut only had a cup of coffee in the Majors, appearing in 7 games in 1924 and 1 game in 1925, all for the Cincinnati Reds. So it's clear these were made specifically in tribute to Cubans who played in the Majors, even for only a few games. They were likely produced in the mid-1920s.