The contessa of counterfeit arrives at the door of a swank Washington restaurant, pulls her 4-foot-11-inch frame up to buss the blushing maitre d' and is whisked through the throng to her table.

"Honey, I'm responsible for more cheap weekends than any madam in the country," says Helen Ver Standig, better known as Madame Wellington, the 62-year-old Washington widow who claims to be the world's largest diamond swindler.

Her voice sounds like the aftereffect of gargling with gravel. Her salt-and-pepper hair is pulled back into a conservative bun covered by a custom-made pillbox hat. On the fourth finger of her right hand is a rock the size of a jawbreaker.

"Of course it's a Wellington," she says in mock indignation.

She slips off the ring and holds it up to the light. The crystal gem sparkles brilliantly -- an ice cube set aflame. It looks like a diamond. It feels like a diamond. And, as Madame Wellington tells her customers, if you think it's a diamond, well bubbie, it is a diamond.

"We had a very prominent woman in New York whose husband is a very prominent publisher," she confides, taking a Kent from her gold cigarette case and lighting it with her gold lighter. "She brought in a diamond bracelet that had 42 three-carat marquises on it. I know damn well that bracelet had to be worth a million dollars. Well, we're right across from Van Cleef & Arpels. She went over to them, had them remove the stones and then came back for us to replace them with Wellingtons."

Why couldn't her store remove the diamonds?

"Because my girls wouldn't know a diamond from a Wellington! Are you crazy? Neither would I."

A wisecracking, back-slapping, saavy businesswoman with a mischievous grin, Helen Ver Standig acts as if she had pulled off the most preposterous practical joke on the rest of the world. In fact, she has. Spurred on by the high price of real diamonds, increasing crime and skyrocketing insurance rates, the ersatz ice biz is booming. Especially in Washington, where the Reagan administration has lined up so many Heavy Glitters.

"Business is great because they have more parties," Ver Standig says. "We've definitely noticed an increase."

What started out in 1966 as a tongue-in-cheek mail-order marketing idea has grown into a multimillion-dollar business, with eight retail stores across the country (Washington, New York, Chicago, Philadelphia) and 200 employes. Now there is even a Wellington in a museum. In January she donated a 34-carat pear-shaped pendant necklace to the Carnegie Museum of Natural History in Pittsburgh.

This year, Ver Standig, who teaches marketing at the Wharton School of Finance at the University of Pennsylvania, was the first woman recipient of the prestigious Joseph Wharton Award for her contribution to the world of business. She also owns four radio stations and a resort hotel on Cape Cod.

"I'm not a golfer or a tennis lady or a bridge lady," she says disdainfully. "All I know how to do is work and have a good time."

She drives a gray Mercedes (license plate: "MME W"), a 1964 Cadillac ("It's in MINT condition. I keep it better than my body"), discos at Pisces, lunches at Mel Krupin's, shares her Rock Creek Park house with two maids, five dogs and a cat and says she travels "any damn place I want to go." Usually, it's La Costa in January, Palm Beach in February, St. Croix in March and Cape Cod for the summer.

"Hell, I've made a lot of money," she laughs.

She sells the $150-a-carat counterfeits (as opposed to the average $40,000-a-carat flawless diamond) to bankers, lawyers, actresses and actors, playboys, businessmen, housewives and heiresses. She says a small foreign country recently purchased a Wellington tiara (which retails for $25,000).

Ver Standig claims she once sold a pair of fake diamond drop earrings to the White House, though she won't reveal the name of the first lady.

"I don't think it's fair to reveal the names of my customers," she says, sipping Chablis and lighting up another Kent.

Singer Jane Olivor, while appearing at Wolf Trap, reportedly bought a $200 pear-shaped pendant last summer at the Wellington store in Tysons Corner.

"Strangely enough, it's a very secure person who buys a Wellington," the madame says. "They're emotionally very secure."

Still, she says, keeping the identity of her customers a secret is vital to the success of her business. Even the jewelry boxes are unmarked.

"Do you know how catty people are?" she says. "They'll call up and say, 'My name is Mrs. Montgomery Axelrod the Fourth. Do you have my ring ready?' Let's say they see you walking into the store. They'll call and ask if your ring is ready, hoping against hope that the salesgirl will say yes.

"They're miserable people," Ver Standig groans.

Another glass of Chablis. "I'll give you a good example. I went to this charity thing yesterday and met a very social lady. She's got an 11-carat diamond and -- this is top secret, she says -- would I copy her diamond? She doesn't want to wear the real thing. She's too afraid. But she doesn't want to go into the Wellington store because she's afraid she'll be recognized. Would I do it very quietly? She happens to have a lot of money. She takes me into the corner to tell me all this. It was really nuts."

She puffs on the Kent. "But she could get killed for a Wellington just as easy as for a diamond."

A native of Washington, D.C., 18-year-old Helen Van Stondeg was working in her father's dress shop on Connecticut Avenue one day in 1931 when a tall, handsome man came in. His name was M. Belmont Ver Standig, also known as Mac. The young man from Boston was in town looking for relatives. He took one look at the tiny, voluptuous daughter of the shopkeeper and asked her out for a drink.

Two nights later, Helen Van Stondeg (in dusty rose dress, hat and high heels) and Mac Ver Standig (in white trousers and white crepe-soled shoes) were standing in front of a justice of the peace in Elkton, Md. Ver Standig slipped on his bride's finger a $15 diamond ring he had bought at Horning's Hock Shop in Rosslyn.

"We couldn't wait to jump in the sack," she says. "I'm that kind of person to this day."

When they went back to the dress shop as husband and wife, her parents were angry. "They said, 'Well, you've made your bed, now lie in it,' " Ver Standig recalls.

They lived in Massachusetts for a time before Mac Ver Standig bought a newspaper in Greer, S.C. A year later he sold the paper, tried to enlist in the Army, was rejected because of a broken eardrum and in 1942 moved to Washington, where he started his own advertising agency.

The business blossomed into the largest agency south of New York, with billings of $10 million a year.

Mac and Helen Ver Standig had an unconventional marriage. In fact, they lived together only six months of the year, both keeping separate Capitol Hill homes and a joint residence off 16th Street. That didn't stop them from granting an interview to a magazine that was interested in the happiest couples in the city. "Mac was shackin' up with someone else and so was I," Ver Standig laughs.

In 1961, while on a boat trip to Switzerland, Helen Ver Standig met a scientist who was working with laser beams, trying to develop simulated diamonds using the chemical strontium titanite. Ver Standig loaned the scientist $10,000 to continue the work.

Three years later, Mac Ver Standig developed an aneurysm and he and his wife sold the ad agency. By that time, Helen Ver Standig's Swiss scientist had finished his research on the simulated diamond.

She and her husband took out full-page ads in The Wall Street Journal, selling the fakes for $40 a carat. At that time, real diamonds were worth $5,000 a carat, according to Ver Standig. The response was overwhelming: 20,000 orders within a few days, by her own estimate.

The next order of business was coming up with a classy name for the counterfeits. Mac Ver Standig had always called his wife "Madame," and they ran through a few dozen test names before settling on Wellington.

Next, they commissioned New York Times artist and friend Al Hirschfeld to draw the now-famous caricature of a buxom, tiara'd doyenne of diamonds, dripping with jewels and winking naughtily. Madame Wellington was born.

Some of her tales are as big as the Ritz. "When I first started this business," she says, "I had no idea how many dingbats there were out there. When I opened the Connecticut Avenue store, this guy walks in and buys a 14-carat rock. It was my first sale. We have a 15-day return policy. Ten days later, he walks back in and says, 'This is the greatest thing that ever happened.' Well, he wants another one. Then he wanted to take me for a drink."

They went to the Mayflower, she says, where the customer told her he had spent four days with a "$1,000-a-night hooker." He gave her the diamond. She promptly went out and had it insured. "He said it cost her $2,500 for the appraisal!" Ver Standig guffaws.

"I have this guy in Texas. Every solitary month, so help me God, he buys a 6-carat pear-ring mail order. He gives it to some broad! And every month I get a letter: 'Dear Madame Wellington, It's working. Send another.' "

She throws back her head and laughs heartily. "Can you stand it? 'It's working!' "

Last Christmas, she says, a man walked into the downtown store to look at men's rings. Somehow, he managed to switch a one-carat real diamond for a 3-carat Wellington. He apparently hadn't noticed the words "counterfeit diamonds" in small print on the door.

"Unless they see the sign, they think it's a regular jewelry store," says Ver Standig. She says she had the real diamond appraised and gave it to her daughter for a pendant.

When her daughter married, Ver Standig's son-in-law bought a 4-carat genuine diamond ring. "Everybody thinks it's a Wellington," Ver Standig says. "Poor Joanie. It's killin' her!

"Listen, I used to always have the best table at Duke Zeibert's. One day a man came in with . . . diamonds, so Duke says to him, 'Go over to that woman. She'll know what they're worth.' So I looked at them and said, just kidding, 'These aren't diamonds. These are Wellingtons!' The guy got real mad. He said, 'I oughta shoot that jeweler for having that kind of stuff. I thought it was diamonds I was stealing!' "

Mac Ver Standig died in 1972. "He always said I had the prettiest face and the biggest can of any woman he knew. He was right."

Now, Helen Ver Standig's life is devoted to her two children, one grandchild and her thriving business. No, she says, she doesn't want to remarry.

"Listen honey, I'm just a plain woman. Put that in. I told that to a guy the other day and he almost had a ---- fit."

She crushes out her Kent in the china coffee-cup saucer and flags the maitre d'. Exit Madame of Wellington.