UP FOR AUCTION IS THIS ANTIQUE AMERICAN BRILLIANT CUT GLASS TUMBLER SIGNED BY CLARK.  IT IS A VERY UNUSUAL GEOMETRIC PATTERN WITH "X,S AND O,S" ALTERNATING AROUND THE TOP, AN INTAGLIO CUT FLOWER WITH LEAVES ON TWO SIDES AND AN INTRICATELY CUT DIAMOND ON THE OTHER TWO SIDES.   ALL OF THE CUTS ON THE GLASS ARE VERY DEEP.  IT HAS A 16 POINT STAR ON THE BASE WHICH GOES ALMOST TO THE EDGE OF THE GLASS.    IT IS 4" TALL WITH A 3" DIAMETER AND IS IN EXCELLENT CONDITION WITH NO CHIPS, FLEABITES OR CRACKS.  THERE ARE A FEW SMALL SCRATCHES ON THE BASE FROM USE OR AGE.  IT IS SIGNED "CLARK" ON THE BASE, VERY DIFFICULT TO SEE, BUT IT IS THERE.  T. B. CLARK WAS A PENNSYLVANIA COMPANY FROM 1884-1930, BUT I HAVE NOT BEEN ABLE TO DETERMINE THE PATTERN NAME.  IT DOES BLACKLIGHT THE LIGHT GREEN OF THE AMERICAN BRILLIANT PERIOD.