Stanley Marcus remembers the 1950s, when Benita Downing wrote an order for 2,000 pleated dresses for her department at Neiman-Marcus and needed Marcus' approval for the order. "I'm a gambler, but not that big a gambler," Marcus remembers telling Downing. But he didn't cancel the order, and the store quickly sold the dresses at $59.75 each. Ten years later, says Marcus, the same pleated dress with a price tag of $125 remained a prize seller, with orders coming in from all over the country, and today Marcus' faith in Benita Downing is stronger than ever.

"Binky" Downing, white-haired, with the kindly voice of a grandmother, is the quintessential pro among high-fashion buyers; her insights prompt top designers to seek her approval. Neiman-Marcus makes high profits on designs selected by Downing.

"She has a sweet look but she is strong and determined," says Rosita Missoni, whose knits were bought by Downing when the Missonis first started in business in 1966. "She is the kind of person who knows very well what to do. You don't feel you have to help her."

"She's very civilized," says Karl Lagerfeld. "She's quick. I hate buyers who are slow. That, I think, is the worst."

Downing, 67, lives in the Highland Park area of Dallas and commutes daily to the downtown store, where she has worked for 34 years. But she is as much at home in Paris, where a short time ago she placed the Chloe' order for next fall.

As she sat at a large marble-top table in the Chloe' showroom overlooking a busy corner of the Faubourg St.-Honore', two department managers from Neiman's in California watched her, saying nothing--the decisions are hers. A French woman at her side worked speedily with a hand calculator, giving her cost estimates.

From sketches in a book in front of her, notes on the back of a fashion-show program and clothes on a T-stand nearby, Downing wrote an order for the Lagerfeld designs, among the most adventuresome, influential and expensive clothes made. Sweaters start at $600, silk dresses at $1,500, suits and coats much more; beaded dresses run into thousands of dollars.

Knowing what to buy is the trick. An executive from John Wanamaker nervously bit a cigar. A buyer from a New York boutique, hunched over her note pad, anguished over her selections. Buyers from Switzerland, Munich, Riyadh and Taipei wrestled with their choices, stealing glances at Downing's table.

"To other buyers I have to suggest things," says Christine Jobert, Chloe''s vendeuse for export customers and Downing's co-worker. "With Mrs. Downing, I'm just listening." Later Jobert adds, "When others ask me what are my best sellers, I look at Mrs. Downing's order. She will have found them."

Downing started working in the shop of a Dallas neighbor when her husband was reported lost in action after Pearl Harbor. The store was two blocks from her house, and she could get home for lunch with her two small children--a son who is now first secretary at the American Embassy in Peking, a daughter who is married to a rice farmer in Bay City, Tex.

Once her children were in school all day, Downing accepted Stanley Marcus' offer to work at Neiman-Marcus. She had known Marcus' late wife, Billie. "After three weeks he made me the buyer of his three largest departments. I didn't even know how to fill out the forms," she laughs. "I took Latin all through college to skip having to take math."

She began scouting the European markets 26 years ago for things that weren't available in New York. There weren't any shows. "You went around from place to place looking for new things, and if you didn't find them in one place you moved on to Sweden or Portugal, wherever," says Downing.

Now, as then, she'll see something she can't resist buying for herself. But she is cautious. "I have a very sensible family, and they were inclined to feel that if you dwell too much on the subject of clothes per se, this was very superficial and not very nice. You always had to find some way to justify it, perhaps as an art form or by knowing something of its history." She once researched the history of Chinese robes Stanley Marcus bought for the store. "The history was interesting, but the only reason for buying them, Mr. Stanley said, was because they were beautiful."

There is only one standard for buying something, says Downing. "It has to be beautiful," she says. "I'd reject something because it is too expensive for the social life of an area, but nothing is too expensive if I know what its place is."

Downing even insists there was beauty in the punk styles by Zandra Rhodes during the late '70s--hand-painted dresses with silver safety pins and chains--that created a storm of protest when displayed in Neiman's windows on bald models. "There were women who felt those dresses expressed the way they felt," she says. "That made them right."

Downing recently at work:

She arrives in Paris from Milan on the Sunday before the Friday Chloe' show. On Monday, after lunch in a new Chinese restaurant that Chloe''s Christine Jobert has discovered, Downing is shown thumbnail-size swatches of the new fabrics and working sketches.

Downing is one of the rare buyers allowed to browse upstairs in the Chloe' workrooms as designer Lagerfeld works on the final pieces for the show. Bolts of specially created fabrics are stacked floor to ceiling in one room. In another, a dozen women are hand-beading dresses. Lagerfeld, wearing a white chemist's coat, is pinning fabric in a blouson shape on an assistant.

"You like it?" the designer asks Downing, looking for her approval. She smiles and asks what it will be. Lagerfeld explains, tells her why he has chosen the deep gray color, the blouson shape. She smiles again, clearly pleased.

Friday morning Downing is in the front row at the Chloe' show, the row usually reserved for store presidents. As the models parade out, she makes a list on the back of her program: "big black hat, black coat, long black dinner suit, Mondrian applique's, black boots, black hose . . . "--two columns of clipped descriptions, references for when she writes her order.

At 9 the next morning she is back in the Chloe' showroom, getting an exclusive look as owners of Chloe' boutiques from around the world ask for their favorite choices to be modeled informally. She takes notes again, singling out the styles she wants to be sure not to miss. That night, almost through the night in her hotel room, she balances sketches, lists, color swatches and categories, making choices so that she won't overload on suits or dresses, for example.

Sunday morning Lagerfeld has forgotten to advance his clock for Daylight Savings Time and arrives at the Chloe' house an hour late for an appointment. Downing is already there, writing her order. "I am embarrassed. I knew Mrs. Downing would not forget the time change," says Lagerfeld.

She makes her selections. One is a blouse with a scarf "because people are looking for a unique neckline"; she likes the dolman-sleeved coat "because it fits over everything"; picks a black wool blazer with Mondrian embroidery on the pocket "because a woman can own it for a lifetime"; a knit dress "because for $500 or $600 a woman can start to own a Chloe'." She chooses a dress with a bib front "for the woman who wants to wear good, good jewelry." A sweater "is simple enough to go under everything, that makes it important. If you don't have all the parts the whole sale can go by the boards."

By 4 o'clock, 48 hours after the show, Downing is finished. She shuts the book on her order. She has also selected the clothes and accessories for newspaper ads and the store's Christmas catalogue. The decisions made, she will have no second thoughts. "It's a package and it is done," she says.

Without fanfare she leaves the house. The buyers who started with her are only halfway through their orders.