Now showing: the private life of Marilyn Monroe?

It could have been a scene out of “Ocean’s Eleven.” A luxury cruise ship, armed security guards, hidden cameras and a locked vault. But inside was not an internationally known cache of heist-worthy gems but another kind of enduring curiosity -- jewelry and other items said to have once belonged to Marilyn Monroe:

* A pre-engagement garnet ring given the movie legend by New York Yankee slugger Joe DiMaggio in 1953 -- the exact ring his mother had worn but resized and with the inscription “MM” added.

* A white jade bracelet with 24-karat gold that DiMaggio gave his wife on their trip to Japan in 1954.

* A gold powder compact with a miniature clock embedded in the case with an inscription from DiMaggio: “Marilyn, I hope this helps keep you on time. All my love, Joe.”

Other items from “Marilyn Monroe: The Exhibit,” which goes on display today at the Queen Mary in Long Beach, veer from sentimentality straight into voyeurism. For $22.95, the public can ogle intimate items from Monroe’s boudoir, such as a pair of her panties, a bra and even a girdle.

This being the world of Monroe enthusiasts, there is controversy, of course. Sight unseen, rival collectors already are questioning the caliber of the collection and whether Monroe actually wore some of the items displayed. And they are wondering aloud about the man behind the exhibit, Robert W. Otto, a 55-year-old Chicago collector. Otto, a low-key fellow with a polished spiel and the manner of a Midwestern grocery store manager, gave The Times a preview of the collection this week that included a visit to the “Joe and Marilyn Room,” featuring items such as the nightgown Marilyn wore on the night of her wedding to DiMaggio as well as her wedding gloves and handbag.

Otto’s collection also features lipstick and hair curlers, along with jewelry, dresses, gowns, a pair of mother-of-pearl sunglasses from Italy, mother-of-pearl opera glasses, nylons and a mirror with an image of a girl on the back that Otto said Monroe took everywhere with her. In a room on the Queen Mary’s sun deck is a collection of Monroe dolls (one wearing a real miniature mink stole worth $5,000) and also a display of wines marketed with Monroe’s image.

Some of the rival collectors say Otto is something of a mystery man in their world. They say that until last year, they had never heard of Otto. Then he seemingly came out of nowhere to stage a Monroe exhibit in Indianapolis with the cooperation of CMG Worldwide, the company that licenses the names and likenesses of many dead celebrities, including Monroe. The critics also question the uniqueness of many of the items on display at the Queen Mary, given the fact that her memorabilia has been out there for years.

“He talks about he has all the wines, well so do I,” said Greg Schreiner of the Marilyn Remembered fan club, which each year stages a ceremony at her crypt on Aug. 5 commemorating her death in 1962. Otto has “lots of magazines, so do I.” And, he noted, there is no indication that any of the clothes on display at the Queen Mary were worn by the actress in her films.

Schreiner and other collectors recently loaned some of their most treasured Monroe keepsakes to the Hollywood Museum, where they are on display. They include movie costumes, makeup, rare photos and furniture from her home.

“We never made anything off of this,” Schreiner said. “We do it all because we love Marilyn.”

Otto said he began collecting Marilyn memorabilia 37 years ago after he got into the business of collecting DiMaggio keepsakes. And if none of the other collectors have heard of him, Otto says, it’s simply because he kept a “very low profile” and concentrated on courting those people who actually knew Monroe and acquiring items from them.

“I also chose not to collect the bigger show pieces,” he added. “So I’m not with Debbie Reynolds trying to buy one of the big gowns from the show stuff. It’s a lower-profile collection.”

As for the lack of movie memorabilia, he added:

“This is really a private, up-close tour of Marilyn, and it is kind of devoid of all of those big, splashy gowns and the big movie pieces. There’s a couple of pieces, but I’m not that wealthy to afford all that.”

Mark Bellinghaus, a Los Angeles collector who has a house filled with Monroe collectibles, scoffed at what he knows about Otto’s collection. Bellinghaus’ holdings include Pucci blouses (some with sweat stains), furniture and paintings that graced the actress’ home at the time of her death (he even has preserved in a plastic bag a hair curler with a blond strand of hair attached to it that he is convinced came from Marilyn’s head).

“Most of [Otto’s] items are tacky,” Bellinghaus said, and he scoffs yet again at the suggestion that Otto has the world’s biggest Monroe collection.

For his part, Otto said he did not claim he had the largest collection, noting that was a statement made by an official with CMG Worldwide.

For Otto, the Queen Mary exhibit is a for-profit venture, the first leg of a world tour that he said would include 39 cities on six continents and probably take 10 to 12 years to complete. Once that is over, he hopes to place the collection in a Monroe museum. “There is no museum for Marilyn right now, and that’s where all of this is going to go,” he said.

Otto explains that he doesn’t go after the items that Marilyn wore in her films, like actress Reynolds did when she acquired memorabilia from the old MGM studios for a proposed museum. Instead, he said, he’s specialized in collecting items that Monroe used in her private life.

“The bottom line is, I’m not buying and selling, or trading” in memorabilia, he said. “That’s where you get in with those” other collectors.

The bulk of the items on display at the Queen Mary came from June DiMaggio, the niece of Monroe’s second husband (she was scheduled to participate in a panel discussion at the exhibition Thursday night), and from TV talk show host Joe Franklin, according to Otto.

“Those are two major sources” of the collection, Otto said. “You’re probably looking at 90%” of the exhibit.

A dress that Monroe apparently wore when she was known as Norma Jean and that Otto acquired from Franklin is a case in point. Otto said the story Franklin told him was that Monroe one day threw open her closest and invited the TV host to take anything he wanted.

Otto acknowledged that the soaring value of Monroe memorabilia in recent years had resulted in fakes flooding the marketplace, but he insisted that if he had any doubts about an item, he wouldn’t display it.

Each of his items comes with a certificate of authenticity, but other collectors say that unless an item comes with a photograph of Marilyn wearing that item, people should be cautious. They also note that certificates of authenticity can be forged.

Asked why the items on display aboard the Queen Mary didn’t have photos showing Monroe wearing them, Otto said that like with anyone else, the clothes Monroe wore in private didn’t often appear in photos.

Otto, who is the chairman and chief executive of a company in Chicago called Marilyn Monroe Exhibits, said he was convinced after talking to people who knew Monroe that she wouldn’t have minded display of her personal effects.

“I talked with several people who knew Marilyn and all of them said, ‘Bob, if you want to do a tour of this for profit, Marilyn would love this.’ I said, ‘Are you absolutely sure?’ I asked June DiMaggio. I asked Joe Franklin, [and they told me] Marilyn likes her things to be shown. [June told me] Marilyn’s a peacock. She said, ‘Bob, I kept all of this stuff. I have it all, but I can’t think of anybody I’d rather sell it to than you because I know what you are going to do with it and Marilyn Monroe would love this.’ ”

Otto went on to say: “I have never sold one piece that I purchased of Marilyn Monroe. I don’t collect things and buy things to sell them for higher profit. Never did it and never intend to.”

He refused to say how much he paid for the items, but noted that some have said that the items on display might be worth as much as $10 million.