records as of 15 May 1995
Anthony Gatto flashed 12 on June 22nd, 1993 at the Wintergarten in Berlin. Photos in _Kaskade_ 31, 9/93, p.28, and _JW_ 45.3, Fa.'93,p.8. Albert Lucas flashed 12 (in _Guinness_). See photo in _Juggler's World_ 36.3, Fall '84, p.19, and then send me a copy! Jian Wen Qian flashed 12 in practice.
_Circus Techniques_ by Hovey Burgess (reprinted '89) mentions on page 46 an account of a woman juggling 12 rings in ancient Greece (_The Banquet_ by Xenophon, translated by O.J. Todd, Cambridge : Harvard University Press, 1922). From "4000 Years of Juggling", by Karl-Heinz Ziethen (Vol. I, p. 8), the banquet is "at the house of the rich Athenian Kallias (422 B.C.)," and is visited by a Syracrusanian troupe which included a girl juggling with 12 hoops while dancing.