The same week that New York publicist Barry Landau became a corroborative witness against White House Chief of Staff Hamilton Jordan in the Studio 54 cocaine-sniffing allegations, Landau received between $10,000 and $12,000 through the efforts of attorney Roy Cohn and a Cohn associate to help pay deliquent bills and finance a vacation for two in Acapulco.

Landau told The Washington Post several months ago that the money involved was his own, representing the sale of his jewerly which, on the instructions of a then-associate in Cohn's firm, was taken out of pawn by a third party and sold to a jewler.

Landau has denied in a succession of interviews that the assistance Cohn's firm provided had anything to do with a sworn statement he gave Cohn in August 1979 to support allegations made against Jordan by two of Cohn's clients, Studio 54 owner Ian Scrager and Steve Rubell. Landau had said in his sworn statement that Jordan had asked him at Studio 54 "where he could get some coke."

But it is known from several sources that special prosecutor Arthur Christy has been looking closely into the circumstances surrounding the money, which passed to Landau within a matter of days after Landau's statement was made public.

Christy's mandate includes determining whether false statements had been made to the Justice Department during the preliminary investigation of the allegations against Jordan.

On Friday, Christy interviewed David Grippe, a client of Cohn's who was convicted in federal court in 1977 of transporting stolen property. Grippe has acknowledged to The Washington Post that he acted as a go between in disposing of Landau's pawned jewelry.

Landau spent 2 1/2 hours before a grand jury in New York on Friday and was scheduled to return yesterday. Grippe, who says he has not yet been called to the grand jury, was interviewed by Christy at 3 p.m. on Friday.

Grippe confirmed yesterday that he had been interviewed in detail about the jewelry and money orders which were used instead of cash in the transactions.

According to what Landau has said in previous interviews, Roy Cohn had expresed concern to him about "anything that might be used to discredit me [Landau] as a witness."

When Cohn learned that Landau was "temporarily short of funds," Landau says, Cohn instructed a then-associate in his firm, Roy Kulcsar, to "find a way" to clear up his debts and bring him current in such things as rent and a $500 phone bill.

Landau was also a client of Cohn's, Landau says. The firm was representing him in the breach of a public-relations contract with a Manhattan restaurant owner.

In a review of his assets, Landau says, he and Kulcsar decided to redeem jewelry that Landau had pawned for $4,500. The jewelry was appraised at $28,000 and had been in the pawn shop "a long time," Landau says. a

Grippe was given an advance of $4,500, in money orders, and sent to a "jeweler Roy Cohn Knows." Landau was then told that the jewelry was sold for $12,000.

Grippe, who owns the King's Plaza Carpet Shop in Brooklyn, had installed $2,000 worth of carpet in Landau's apartment sometime earlier, according to Landau. After subtracting what was owed him, plus the $4,500, Grippe delivered the rest of the $12,000, Landau says.

According to Landau, Kulcsar gave him $3,000 worth of money orders, which he took to a travel agent "Cohn uses." Landau says he bought two tickets to Acapulco for himself and a friend and "cashed the rest for traveling expenses."

Landau says he had to get out of New York because he was under siege by the media after it became known that he had given the statement about Jordan.

Landau told a reporter several months ago that it is not clear to him what happened to the rest of the $12,000.

Roy Kulcsar declined yesterday to comment on anything pertaining to Landau, Grippe or himself.

An attorney-client relationship existed between him and Landau during the time under discussion, he said, and still exists between him and Grippe.

Roy Cohn did not return phone calls.