In addition to posts #31 and 32 above, I have added two images of the array of some of the many hundreds of unusually heavy Thirty Years War clay grenades dug up in Ingolstadt, Bavaria, in 1983.
I also added an image of glass hand grenades, French, ca. 1740, found in Freiburg, and provided a link to the Wikipedia survey:
http://en.wikipedia.org/wiki/Hand_grenade
Best,
Michael