This master marble is from Mark's Geometric series, each one of these a sweet piece of marble history! AND, this marble is EXTRA SPECIAL, as it was inspired by warning and caution symbols, and designed in response to the 9/11 attack on the World Trade Center. Each has both poles finished to a perfect closure. Mark refers to this as having “2 North Poles.” These yellow Warning and red Danger Balls are very rare and seriously hard to come by! These incredible patterned marbles are made using the graal technique, with black glass layered over yellow (in this case) and then the pattern meticulously laid on the marble and blasted away, then completed with a thick layer of crystal dipped and laid over the pattern which makes the whole thing absolutely pop in hand. Signed 'Matthews 2009'.