So I wonder if this thing (and perhaps what you saw) was an acrylic shell made to look marble-ish? I didn't see the article, so I don't know what you saw...did it actually look like solid marble?
a bit of background -- the "Musik Messe" is like a NAMM show, in Germany. Every product in the photospread looks like new stuff, yet to hit the market. So for something to be labeled "stone drums" at this event is probably an aptly-named attention getter.
The acrylic drum seen in your ebay link, whose "grain" is milky, is quite different from this STONE DRUM, whose grain is straight, vertical from head to head. And the telltale sugary texture of marble is evident, even in that little pic. No seams or couplings holding the shell together -- it looks like a solid piece of stone, w/ standard lugs & throwoff fastened in the usual way.