For three months this summer Deborah Masten, 33, who carries the cumbersome title of district merchandise publicity coordinator for J.C. Penney, was one of seven people who knew that royalty would descend today on Springfield Mall.

In the midst of her critical and crazy countdown last week, Masten, a diminutive blond as poised soft pretzel.

It's a holiday and a sale day and Penney hopes to have the store open for the expected crowds by 11:30 a.m.

Masten, a former Jefferson, Ind., schoolteacher and lifelong Anglophile, is logistical mistress of the event and has barely slept in the last two weeks. When she has, she's dreamed of each step and stop the royal couple will take once their limousine pulls up at the store after the 15-mile drive down Interstate 95 from Washington.

At 10:05 the motorcade pulls up, she said. "David Miller, president of Penney, and William Howell, chairman of the board, will go out to the limo and welcome the couple. They will come in this door. The red carpet will come here. There will be two dozen roses on each side of the greeting area." The racks of pink-and-white fake furs will have been moved. The first of four platforms of 30 press representatives will be poised with tape recorders, pads and cameras.

After brief remarks by Miller, Charles and Diana will walk past more fake furs, the Halston III petites and the seven-foot replicas of Buckingham Palace guards, and pause at the first exhibit of British goods -- outerwear for women by Sheridan Barnett. There they will chat with Cyril Kern, the chairman of Reldan Ltd. and chairman of the British Fashion Council. After a slight right turn, they will pause at the display from the Royal Mint Stamp Collection, which includes a stamp of Queen Victoria canceled with a black print and a red Maltese cross. Behind the stamps are replicas of some of the crown jewels. Then they will walk past the Penney Diamond Collection, pause at a doll of Queen Elizabeth I created by area artist Patricia Diaz and then pass by an exhibit of historical British costumes.

Heading toward the men's department, past the tights and umbrellas, the couple will see the popular six-foot Emmett Rolland Golf Fantasy Machine. Then past the men's briefs, terry robes and handkerchiefs to the men's suits, where James Bradford, president of DAKS United States, will answer any questions. The prince, according to Penney, already buys the DAKS line.

Next, on their way to a Rolls-Royce, balanced -- to prove a point -- on four Wedgwood coffee cups, the couple will pass the junior sportswear department festooned with Lee jeans, "Experience in London" tops and Miss Selfridge sweaters and paisley blouses. "We are hoping that this will be a 'touchy-feely' point for Her Royal Highness," said Masten, alluding to Princess Diana's celebrated flair for fashion. In the area where the Rolls is parked, Chairman Howell and President Miller will give Their Royal Highnesses a quilt, specially made by fifth- and sixth-generation quilters, in a Pennsylvania hex design centered with an American eagle. Included in the pattern are oak leaves and acorns for courage and fidelity, stars for luck, success and happiness, and hearts for love.

No public remarks are planned by either Charles or Diana, but Masten is crossing her fingers. "This is an occasion that would lend itself to some comments. And when they leave here, they go back to the embassy, so they aren't in a hurry."

Whether or not a royal quote develops, the couple will take a last seconds-long stroll past the replica of a British bus front, the pink blouses and the blue and pink sweat suits. There will be no time to walk through the rest of the mall and get a slice of pizza from the Orange Bowl or send a card to Mum from Sentiments Hallmark.

The question that people are asking is 'How did Penney do it?' In snagging a visit by the royal couple, the third-largest retailer in the country has shown how seriously it takes the slogan adopted in 1984: "We're looking smarter than ever -- J.C. Penney." One Penney executive put it simply: The store spent $50 million on British merchandise, now on display in its 500 stores. The royal visit benefits both the store and Britain, said Joseph Canzeri, the former Reagan detail man hired by Penney in August for the predicted onslaught. "Here is something American that everybody knows and goes to."

Like many other retailers, Penney has moved in recent years to upgrade its image. Starting in 1982, it has evolved gradually into a high-tech, carpeted merchandise mart attracting the goods of mainstream designers. A major remodeling of the Springfield store was completed earlier this year. With 100,000 square feet on its first floor alone, the store is one of the top five Penneys in terms of sales volume. Joining another trend of modern retailing, Penney has organized international theme shows. In 1984 it was Italy.

What evolved this year was an event of planetary proportions.

While buyers for Penney were making 100 trips to the British Isles and coordinating with the British Embassy and the British Trade Commission, an embassy contact mentioned there was a possibility the royal couple would be traveling to Washington. "When they became aware, they mentioned it to us, and we said we would be delighted if it could be worked out," said Patricia Starr, a Penney executive. "But we didn't count on it."

A few weeks later the embassy said it would like Penney to submit a proposal. That was followed by a visit to the store by several embassy and palace officials. In March, Masten and Karen Edds, manager of merchandise publicity and special marketing events, wrote the proposal. That was followed in early May by a "reconnaissance visit" by Prince Charles' secretary, who, recalled Masten, "just wanted to know what they would see." The Springfield store was selected by Penney because of its proximity to Arlington National Cemetery, originally the next stop after the store.

In June the store found out it was granted the visit. No letter was exchanged, just a verbal agreement. "We never received a letter or anything that I could frame," said Masten. "We just went ahead." In August the meetings were once a week. Then, just after the story broke about the royal visit, the interest in Penney swelled. "That's when the phones started ringing," said Masten.

Penney officials considered having the prince and princess visit while the store was conducting business as usual, with cash registers and bells ringing, clerks checking credit cards, the gridlock of baby strollers and the rubbing of polyester and cotton shoulders.

"That lasted five minutes," said Masten. "We were afraid someone would end up getting hurt." The mandate of Penney, explained Canzeri, was to have the visit "be as dignified and as open and available as possible."

Two hours before the arrival, Penney employes will meet with Masten and store manager Frank Michela to brush up on the protocol and check any last-minute details. Up to now they have received a newsletter in their paycheck that described etiquette and security and have had one background session. "We've told them they can't move, they must remain in their assigned area. They can't stand over or reach across the dark rim of the carpet," said Masten. They have also been told "not to offer their hand unless one is offered to them, and no photographs," she said.

On a bulletin board at Springfield Mall, the management has put up for the uninitiated all the clippings of stories about the royal couple. "I never got interested until I learned they were coming. We are all happy they picked Penney's. And all the customers are talking about it," said Steve Saunders, 21. If the royals walk in his direction or speak to him, Saunders said, "hopefully I wouldn't faint."

In the coat department Roslyn Handler, a saleswoman for 11 years, had already survived three national interviews by last week, had picked out her blue Ultrasuede suit for the visit and was predicting today would be "the most exciting thing that has happened to the store and to me." She described herself as over 50. In accessories, merchandising assistant Judy Kicker, 22, who said her uncle had been Prince Charles' "sports master" at Cheam School, "fixed up the hat display, since Lady Diana loves hats. And we have been cleaning." "We clean all the time," corrected Betsy Leonhard, a senior merchandising manager. "We are just putting a little extra into it."

Checking to see if the store had hung its Union Jacks properly -- the thicker white band should be at the top -- was Cynthia Goldstein, a British subject who lives in Alexandria, and her niece Rachel Elson, who, like Princess Diana, is visiting America for the first time.

"For the queen's Silver Jubilee in 1977 we queued up at 3 a.m. We don't plan to get here that early. But Diana is the only one I haven't seen in person," said Goldstein. "She is the princess of our dreams," she said, adding confidingly, "Prince Charles needed someone young."

And if perchance the couple want to purchase something "off the peg," as they say in London, Masten said, Penney is prepared, even though the computers will be turned off. "We would take care of it the old-fashioned way with a sales slip."

The biggest crunch -- literally so far -- has been the mating of two symbols of British elegance: a white and beige Rolls Silver Shadow and four white Wedgwood demitasse cups. The first round of cups broke from the weight of the 6,056-pound sedan. "We swept them up and started a cup call," said Canzeri. The final installation, which required 12 hours, left the car resting on wooden planks on top of the cups.

At 7 p.m. yesterday a crew started to install the parking lot barricades. At 9:30 p.m. a final walk-through was scheduled. Then the first of two security sweeps. At sunrise a crew from Amusements Unlimited was to begin inflating the 5,000 balloons.

Penney is trying to make sure the press is pampered, instead of pushed and stampeded. "Everyone," stressed Canzeri, whose office has been assisting in the logistics, "came up with the idea of having an English butler serve tea to the press." Cable News Network will carry the arrival and departure live.

The highlight, said Canzeri, will be 11 a.m. today when it is all over. He remembers countless ceremonial headaches at the White House that prepared him for this occasion, which he compared to the welcome home for the Iranian hostages.

But nothing in Masten's life has prepared her for this. In normal times she peddles stories about Penney promotions and products to the press in Washington, Baltimore, Frederick, Md., and Fredericksburg, Va. "It is enjoyable," said Masten. "But this is completely different. I am usually knocking on their door; now they are knocking on mine."