This peculiar object in the British Museum, Dept. of Britain, Europe and Prehistory, is a form watch. It was made around 1650 by Wilhelm Peffenhauser in Augsburg (Germany). It is described as “gilt-brass and rock crystal cased verge watch in the form of a snail, with leather outer box” .
The snail is shining through like it is a thin-shelled living animal. Thus a beautiful piece of craftsmanship. As a whole, it seems to be modelled after a Helix-like species; the shell is dextral.
 BML, inv. [BEP] 1888.1201.197. http://bit.ly/1iJma0w.