Has David Geffen flip-flopped? Word has it that he’s quietly shopping the twelve-room duplex he bought just eighteen months ago at 810 Fifth Avenue. Geffen bought the apartment, which has enviable views of Central Park and once housed former New York governor Nelson Rockefeller, for slightly north of $30 million and secured the approval of a co-op board that reportedly took its time about interviewing him. Now, a source says, he may have decided he doesn’t want it after all. It doesn’t look as if he ever moved into the building, a gracious thirteen-story affair that at one point was also home to Richard Nixon. One possible buyer if Geffen does decide to sell? Peter G. Peterson, chairman of the Blackstone Group and former head of the Federal Reserve Bank of New York (and a Nixon cabinet member!), who’s said to be eyeing it.