DALLAS (AP) — Long-hidden items and documents related to the 1963 assassination of President John F. Kennedy were revealed for the first time Monday, after spending nearly two decades locked inside a courthouse safe.

Dallas County District Attorney Craig Watkins presented the articles at a Presidents Day news conference while standing next to brown and white file boxes stacked in a pyramid.

Tony Gutierrez/STF (ENLARGE)

AP photo Dallas County District Attorney Craig Watkins addresses the media as he presents some historical documents and other memorabilia, in boxes to left and on table, connected to the assassination of President John F. Kennedy during a press conference in Dallas Monday.

The items include a purported transcript between Kennedy assassin Lee Harvey Oswald and his killer, nightclub owner Jack Ruby; a leather gun holster that held the gun Ruby used to shoot Oswald; brass knuckles found on Ruby when he was arrested; and a movie contract signed by then-Dallas District Attorney Henry Wade.

Watkins said investigators told him about the contents of the blue, two-door safe shortly after he took office in 2007.

"And every DA up until the new administration decided that they wanted to keep it secret," he said. "What we decided, that this information was too important to keep secret."

One of the most intriguing items was the typed transcript of an alleged conversation between Oswald and Ruby. The transcript — which hasn't been examined by experts and has already been called farfetched by some — includes talk of killing the president at the behest of the Mafia.

"Now we don't know if this is an actual conversation or not," Watkins said. "But what we do know is that as a result of this find, it will open up the debate as to whether there was a conspiracy to assassinate the president."

Ruby killed Oswald on Nov. 24, 1963, two days after Oswald was arrested in the assassination of President Kennedy. Ruby was convicted and sentenced to death the following year. Ruby won an appeal of his conviction but died of cancer before he was retried.

The two-page transcript resembles one published by the Warren Commission, which investigated Kennedy's assassination and determined Oswald was the lone gunman.

In that report, the FBI concluded that a transcript of an alleged conversation between Oswald and Ruby was fake, and that it had been "re-created" for authorities by a now-deceased Dallas attorney who claimed he recognized Oswald in a newspaper photo as the man he saw talking to Ruby. The reconstruction alleges the men discussed killing the governor, but the two didn't name then-Texas Gov. John Connally.

The transcript Watkins showed Monday is also from Oct. 4, 1963, and allegedly happened at the Carousel Club, a Dallas nightclub. It begins with a discussion of how the "boys in Chicago" want to "get rid of" U.S. Attorney General Robert Kennedy, JFK's brother.

"There is a way to get rid of him without killing him," Oswald says.

"How's that?" Ruby responds.

"I can shoot his brother," Oswald says.

After a discussion of the logistics of shooting the president, Ruby says the money for the operation's coming from the Mafia.

"Are you with the Mafia?" Oswald asked.

"You're asking too many questions," Ruby responds.

Later, Ruby gives a lengthy warning that Oswald must not get caught or say anything, noting that "if you do talk, then the boys will make me follow you, wherever you go, and kill you."

Gary Mack, curator of the Sixth Floor Museum near where the president was shot, thinks the document displayed Monday could be one of many scripts written for films about the assassination.

Staff from the DA's office were nearly finished scanning the scores of typed and handwritten papers and cataloging the items. Recordings and films kept in the safe had not yet been examined. Once the task is completed, Watkins said his office plans to turn over the articles to an organization that will continue making them public.

"We're looking forward to the opportunity to talk with the district attorney ... We would love to have these records," Mack said.