The Wurlitzer Mandolin Quartet (circa 1906) is dominated by its reverberating mandolin. Its distinctive sound is created by tiny metal mallets that directly strike the piano strings, complimenting the traditional internal piano as well.  

This is another machine manufactured by the Wurlitzer Company.  Notably, it does not have an external keyboard, which likely made it more affordable but also more appealing for their clients, since the only way customers can hear music was by inserting money, which meant more profit than machines with keyboard.  When people who knew how to play the piano came into a facility, they could not perform. Nickels required for music.