I should have read the email telling me about this with more care. When I went to to the recommended page and read about the horse head fiddle in the local history collection at Moyses Hall, Suffolk, I thought at first it was called that because of a similarity in shape: wrong. It's called a horse head fiddle because it is made out of a horse's skull. Apparently it sounds as bad as it looks. Scroll down (right to the end) to see it in all its glory. Alas the picture doesn't enlarge.
Many thanks to Rosemary Hall for telling me about this.