powning chop and sig on mug base ← Previous Next → Peter Powning. Chop, signature and firing/test data? within a base-circle. 1999.. XCIX = 1999; The “P” = porcelain. Peter Powning. Chop, signature and firing/test data? within a base-circle. 1999.. XCIX = 1999; The “P” = porcelain.