Davetnova - According to your description it could be an older form of the zither called scheitholt. It is slimmer than the usual alpine zither, like a long board.

Terry - I remember a guitar in form of a lute,stringed like a guitar, but with a slimmer body and neck. That seems to be a new form of the 20th century for the German youth movement and other folkies. I think Bob figured right.
The original lute has a much broader body and neck and can have up to 11 choirs. It was the usual instrument for house music in renaissance and baroque but lost its importance when the key instruments were available. The lute had no definite fixed tuning; it varied with the songs played.
Goethe writes that he remembered his father seldom playing but mostly tuning his lute. An old joke is: A luthier of 80 years has passed 60 years of his life with tuning.