Tremoloa

Here is another odd instrument that has past through Shonky towers.
It is caled a Tremoloa it is a type of zither or chordaphone.
It was originally made in the 1930's and went through several small design changes. I believe this one originates from the late 40's early 50's.
I bought it mainly out of curiosity and soon found it it was quite horrible to play so sold it on (at a considerable profit ;-) )
It is basically a box made from plywood with two soundholes. 16 strings arranged in groups of four each tuned to the chords in the key of C attached to the left side of the soundboard and a single melody string along the right side. The single string is played with a plectrum attached by a thin metal strip to a heavy metal roller which in turn is attached to the instrument by a swinging arm. When you pluck the string it wobbles the bar and gives a constant wobble to the note.
The best example I found is on This Site