An "appreciation party" where Brooklyn cops got free dinner and drinks — and expensive electronic goodies, in some cases — is now the subject of an NYPD Internal Affairs Bureau investigation, the Daily News has learned. The lavish New Year's celebration was thrown in January 2005 at Manhattan's Prime Grill, where sources said cops were entertained by a magician and walked out with presents and "prizes" in green gift boxes....The affair was hosted by Abe Friedman, an orthodox Jewish leader from South Williamsburg.......On other occasions, revelers were invited to Abigael's On Broadway for a Jan. 6, 2003, bash and again to the Prime Grill on Jan. 5, 2004. All invitations name Friedman as the "host," and described him as an "NYPD liaison."When asked by The News last week about the parties, Friedman said, "I don't know what you are talking about.".."There was a raffle for three GPS [Global Positioning System units]," said a civilian guest at the gala affair. "There were bigger prizes in boxes, but they put them in a room and said they'd get them at quieter times." When The News attempted to slip into the event, men who greeted many attendees by name turned a reporter away. "This is a private party," said the head of the Orthodox security detail, who declined to identify himself. "You are wasting your time. "It's an appreciation party, not just for police, but for whoever has an invitation," he added. The guests were made aware that The News was outside. "They announced that the press was outside taking pictures. They warned the crowd, 'Don't talk to anyone you don't know,' " said the civilian party guest. Some of the expensive electronics, sources said, came from Hello Cellular, a business in Williamsburg that has since been sold. The brothers who owned the store last year initially acknowledged giving BlackBerrys and cell phones to Friedman for the party, but then reversed themselves over the course of a brief interview.