Back in the sixties,a friend of mine bought one----It was quite ornate, made in Germany, and was called a "Miranda". It had sheets of some kind of tab. with it---you slid the sheets under the strings, and then you followed this sort of continuous wavy line, and wherever you saw a dot, you plucked that particular string, and a tune ( probably Teutonic ) ensued.It was much more fun to "clawhammer" it with banjo-picks, to be honest !!