Longish time lurker on account of having nothing to add and a lot to learn, but saw this...
https://www.liveauctioneers.com/item/42441505_antique-violin-an-interesting-violin-with-an-elongated
and wondered what it is and what it sounds like?
Tried Dr Google and found a single example for $750, said to be played Cello style on lap like a Gamba.