College Park, Md. • In the nation's collective memory, the assassination of John F. Kennedy is a clash of images and mysteries that may never be sorted out to the satisfaction of everyone.

But if there is a lasting emblem that sums up Nov. 22, 1963, the day America tumbled from youthful idealism to hollow despair, it is Jacqueline Kennedy's rose pink suit and pillbox hat.

An expanded collection of Kennedy treasures and trivia was unveiled this month on exhibit and online to coincide with the 50th anniversary of his inauguration; it includes the fabric of his top hat (beaver fur) down to his shoe size (10C).

But missing and hardly mentioned are what could be the two most famous remnants of Kennedy's last day. The pink suit, blood-stained and perfectly preserved in a vault in Maryland, is banned from public display for 100 years. The pillbox hat — removed at Parkland Hospital while Jacqueline Kennedy waited for doctors to confirm what she already knew — is lost, last known to be in the hands of her personal secretary, who won't discuss its whereabouts.

Does it matter? Should it? It is said that history takes a generation to decant and great chapters are defined by the trappings of everyday life: a stovepipe hat, a pair of polio braces. Mrs. Kennedy could not have imagined the outfit she put on that morning would come to epitomize the essence of Camelot and the death of it.

This is the story of how an otherwise ordinary pink suit and hat came to be treasured by a nation, only to slip from its reach.

—

Fashion sense • Few public figures understood the power of fashion the way Jacqueline Kennedy did, and when she packed for Dallas, she chose nothing she hadn't worn before. The goal was not to upstage the president, but to accentuate him as the 1964 election season kicked off.

Looking back now at the grainy footage of the first couple as the dark limousine, top down, rounded the turn from Houston to Elm, it's hard not to hope for a different outcome. As long as she is wearing that hat, the world is still intact. Then, inevitably, comes the lurch of his body, the unforgettable flash of pink scrambling in panic across the trunk.

Lady Bird Johnson, wife of Vice President Lyndon Johnson, who was riding in the motorcade's third car, recalled for investigators her memory of Secret Service agents frantic to get the president inside Parkland Hospital while his wife bent over him, refusing to let go: "I cast one last look over my shoulder and saw, in the president's car, a bundle of pink, just like a drift of blossoms, lying on the back seat."

Somewhere inside the hospital, the hat came off. "While standing there I was handed Jackie's pillbox hat and couldn't help noticing the strands of her hair beneath the hat pin. I could almost visualize her yanking it from her head," Mary Gallagher, the first lady's personal secretary who accompanied her to Dallas, wrote in her memoir.

—

For the cameras • Despite urgings from staff and handlers to "clean up her appearance," Mrs. Kennedy refused to get out of her bloodied clothes, according to biographer William Manchester's account of the assassination, The Death of a President.

"Why not change?" one aide prompted.

"Another dress?" the president's personal physician suggested.

Mrs. Kennedy shook her head hard. "No, let them see what they've done."

The suit was never cleaned and never will be. It sits today, unfolded and shielded from light, in an acid-free container in a windowless room somewhere inside the National Archives and Records Administration's complex in Maryland.

"It looks like it's brand new, except for the blood," said senior archivist Steven Tilley, one of a handful of people to lay eyes on the suit since that day in Dallas.

—

Historic image • Yet the suit's stamp on history is indelible for a nation that anguished with every disheveled glimpse of its widowed first lady: climbing the stairs onto Air Force One to accompany her husband's coffin back to Washington, standing beside Lyndon Johnson as he took the oath of office — an iconic photo of an unexpected transfer of power fully explained by a stricken expression and a stained sleeve.

Despite the chaos, aides managed to secure virtually all of the Kennedys' belongings back at the White House by nightfall. The pink hat seemed to hopscotch from Dallas to Washington, according to Manchester's account. .

A White House policeman was told to give it to Hill, but handed it by mistake to Robert Foster, the agent assigned to protect the Kennedy children.

Mrs. Kennedy returned from Bethesda Naval Hospital to the White House in the early morning hours of Nov. 23. She took off the suit and bathed. Her maid, Providencia Paredes, put the clothing in a bag and hid it.

Sometime in the next six months, a box arrived at the National Archives' downtown headquarters. In it was the suit, blouse, handbag and shoes, even her stockings, along with an unsigned note on the letterhead stationery of Janet Auchincloss, Mrs. Kennedy's mother: "Jackie's suit and bag worn Nov. 22, 1963."

No hat.

The box was the one originally sent by the dressmaker, addressed to "Mrs. John F. Kennedy, The White House," but wrapped now in brown paper. Archivists put all of it in a climate-controlled vault, where it remained for more than 30 years.

"It was sort of a secret that we had it," Tilley said. Sticklers for protocol, archives officials knew the suit still legally belonged to Mrs. Kennedy. So it was more than a little awkward when Parade Magazine called in 1996 with a question from a reader asking what became of the pink suit.

And the hat? Hill, 79, the agent who lunged onto the back of the limousine that day to protect the first lady, had the answer.

"I know what happened to the hat," he said in a phone interview. "I gave it to Mary Gallagher."

Reached by phone, Gallagher refused to discuss the hat.

The archives' vast collection includes the president's shirt as it was cut off by the medical team, the tie nicked by a bullet, his white lace-up back brace. Even the contents of Parkland Hospital's Trauma Room One, where he was pronounced dead at 1 p.m. Texas time, are in a cave somewhere in Kansas.

But the whereabouts of the hat is a little-known mystery no one is working to solve; Kennedy historians suspect it was sold to a private collector, or stuck away in somebody's attic, lost to the nation, a hole in history.