Someone recently uploaded a video on YouTube of a rather unusual coin
piano: http://youtube.com/watch?v=Fv7k6qOE-Vk 

It is an "Electratone" piano produced by the Waltham Company of
Milwaukee.  Some of the interior components came from the Monarch Tool
and Manufacturing Company of Cincinnati.  The instrument contains
piano, mandolin attachment, and a reed organ section.  Does anyone know
approximately how many of these units were produced?  I'm assuming this
may be the only surviving example.

Mike Roseboom