** Platinum Asset Management PTM.AX falls as much as 19.1% to record low of A$0.845
** Co says fund-manager Regal Partners RPL.AX no longer considering its takeover amid expectations of a revision to Sept. 26's offer
** Announces special fully-franked dividend of 20 AU cents
** About 4.4 million shares traded, more than 4x the 30-day avg
** Stock down 21.4% this year, as of last close
(Reporting by Nichiket Sunil in Bengaluru)
((Reuters.Briefs@thomsonreuters.com))