A five year old mystery concerning the whereabouts of an eccentric old man's vast collection of artifacts that disappeared around the time of his death deepened yesterday with the completion of contradictory testimony in Prince George's County probate court.

The night of Fred N. Maloofs death in 1972, numerous objects from the collection were removed from his 50 room mansion, Oxon Hill Manor. Yesterday, Maii Maloof, Fred Maloof's nephews, testified that he directed the removal of certain objects for "safekeeping" but later returned them to the bank that had been named executor of the estate.

Maloof who is Calvert county states attorney, has been at teh center of an Agatha Christie-style who-done-it concerning what happened to the estate of his Lebanese-born uncle, an incurable collector of almost everything, including 500 George Washington items alone. "This was an unusual man who left an unusual estate with some unusual people around him," said Jim Kenkel, one of Naji Maloof's attorneys.

Naji Maloof, who returned the items during a grand jury investigation of the estate three years ago, alleged yesterday that other items were taken from the house by a self-sytled curator during the old man's absence shortly before his death. And in the weeks following his uncle's death, he said, even while off-duty state police and sheriff's deputies were working as security guards at the mansion, objects would mysteriously disappear and reappear inside the house.

"Whatever I got was turned over," said Maloof, a giant of a man with a thin, closely-cropped beard. "Whatever I got that belonged to my uncle was turned over to the bank or put back in the house or brought back from wherever it was to wherever it should be."

Lawyers for the former First National Bank of Washington, the Maloof executor, since merged into Union First, contend that there are assets still unaccounted for. "The only thing they (the bank) ever had in mind," Naji Maloof said yesterday, "was not to protect the assets but to put me in jail."

In 1939 when he was short of cash, the elder Maloof negotiated a series of deals with bank officials which left him only with his collections, free lifetime tenancy in the house, and income-producing stock which, his nephew said yesterday, plummeted in market value shortly afterwards.

"My uncle had hard feelings about the bank," Naji Maloof said. "I didn't trust that bank at all and never will." He described a bank official's office as "looking more like my uncle's front room than my uncle's front room did. They had statues and items I remember seeing in my uncle's house."

During this testimony yesterday there were smiles and chuckle from bank people at the hearing. "The record should show they're all sitting here laughing," Najo Maloof said.

After the smiles were gone however, there remained many unanswered questions and a maze of contradictions in three days of testimony before the orphans court.

Maloff and William Harris, his uncle's caretake-chauffeur, testified yesterday that a single truckload of objects was removed from the mansion. This contradicted earlier testimony that six to eight truckloads were reportedly taken in the early hours of April 5, 1972.

Maloofs recollections were fuzzy about some of the items - including valuable tapestries and purported jade and ivory carvings - which had been in the house before the old man died.

Accounting for the Fred Maloof estate has been made more difficult by the lack of clear, complete inventories listing the old man's collections said the one estimate to have numbered 10,000 items. Many items that were not removed from the house at Naji Maloof's direction were later sold in bulk to a New York auction house, which has no itemized list of whatit acquired.

TO try to sort cut the confusion, the orphans court appointed E. Allen Shepherd, an Upper Marlboro attorney, last spring. Shepherd located an inventory allegedly made before the old man's death by Peter Colasante, who describes himself as an art expert and sort of a curator at the Oxen Hill mansion.

Matching Colasante's list against other persons' recollections of what remained in the mansion after Maloof's death and what Naji Maloof ultimately returned to the bank reveals desrepancies, Shepherd and the bank's lawyers maintain.

Naji Maloof yesterday attempted to discredit Colasante, a 29-year old man with a waxed Jerry Conna-moustach who slept unabashedly in the courtroom following his won testimony at a previous hearing on Sept. 8. Colasante was not present yesterday when Naji Maloof said, "I believe, in all honesty, that he or someone on his behalf was entering that house and removing things" before Fred Maloof died.