"I don't regret anything I bought in China," says Jeannette Williams, who accompanied her husband, Sen. Harrison Williams (D.-N. J.) on a trip to China last winter. "Only that I didn't buy more."

Robin Gage, a respected London antique dealer, was stunned by the marine chronometer on display in the antiques corner in the Friendship store in Shanghai last month. It was an exact twin-"even the gold handles were the same"-of the Faberge clock he had admired at a recent Faberge exhibition in London. Only, instead of being in a gold and nephrite box, the version for sale was in a more valuable solid Siberian jade box. He bought it for 3,000 pounds ($6,000), which he estimates is one-tenth the true value of the Faberge piece.

The phone call from the museum mineralogist came as promised. "I'm afraid your necklace is not red jade at all," the expert said. "It is dyed serpentine, the most common stone used for simulating jade."

The People Republic of China is a shopper's paradise. If you are not dead set on making a killing on your purchases, but are looking for inexpensive, unique and therefore sure-to-be-noticed items that are often sensible as well as serviceable and decorative, shopping in China is a ball.

But if you think you are going to pay for your trip with wise buys in antiques, particularly jade, you are a little late. The pros have been in China long before you and have skimmed off the "great finds." They've left some stuff behind, often at high prices.

The essential problem is that those items touted as jade aren't always jade, and "antiques" aren't always antiques, at least not by our definition.

An American gemologist, a past officer in the Appraisers Association of America who has visited China nine times in the last year, says: "Even the Chinese don't always know when something is jade or isn't. And certainly not always what is old jade and what is new."

Asking that his name not be used so that it doesn't inhibit future trips to the People Republic, he explains, "I am brought tray after tray of items that are said to be antique jade. Maybe one in 10 is antique jade, if that many. Some are not even jade," he said. "And of 5,000 pieces of jade that I might see in a warehouse, only 10 are good antiques."

He thinks that shoppers in Friendship stores spending about$300 to $400 for a small carved jade piece such as a horse might well be getting their money's worth. Spending $75 for a small piece, he concludes, is probably not worth the money.

"But what you like and what fits your price limits. And enjoy it," he says. "But if you are planning to make a killing, just forget it."

One recent purchaser of a long, red jade necklace, touted as the last red jade necklace anyplace in Changsha ("The Japanese have bought up every red jade bead but these," the shopkeeper had said), was told they were indeed red jade by two Hong Kong jewelers. One put the value at "$2,500 minimum" for the 200 yuan ( $140) purchase. But, in fact, they turned out to be dyed serpentine, which is often called "jade" by shopkeepers in China.

Red stones, sold as rubies in Guilin (Kweilin) and considered by an American jeweler (who also was a customer in the shop) to be "rubies but not very well cut," turned out not to be rubies at all. "Rubies of this size and color would have to sell for $10,000," a jeweler in the Hong Kong Hotel informed a disappointed tourist who had paid from $14 to $19 for the stones. "Strictly glass," concluded a Washington jeweler.

And a handsome ceramic duck, bought in a store on the Street of Antiquities in Peking, started to dust up before it was unpacked at home. The artist had passed up the final firing.

No antiques older than 120 years can receive the red stamp that gives authorization for the item to leave the country. "You can get far better Chinese antiques in the sale rooms in Europe," insists Robin Gage.

Gage now considers it quite logical that he found the Faberge clock as well as a Faberge inkwell in China. "There were 250,000 Russians in Shanghai before the war," he said. "And it is likely that the Chinese simply had no idea what these were. (As for jade carvings, he says. "The very best stuff I saw was in Hong Kong.")

Many antique experts feel the Chinese are placing antique seals on items 50 years old simply because they feel them worthly of that designation. It has, of course, an advantage for the American customer in that the "antiques" can be taken into the United States duty free. Only recently have some items been stopped by U.S. Customs officers, who questioned the papers and levied duty or held the items pending litigation.

One big problem comes later, when an individual owner dies and Chinese antiques become part of his or her estate. "I'm called in to appraise the estate and I say a jade carving is worth $50 and someone trots out a bill for $800," complains an appraiser who has been in the business 32 years. "They think I am trying to rip them off. And no one wants to believe how badly they have been stung."

There are two main ways to shop for most goods in China. One is at the stores where the chinese shop, the other at the Friendship stores, strictly for tourists. One shouldn't miss either experience.

Not that there aren't ways to spend money every place you turn. There was a small, almost unnoticeable shop tucked in a corner behind the lobby of the Friendship Hotel in Peking where you could buy nifty cinnebar bracelets, boxes and beads, plus carved bone accessories. The lobby of the tourist hotel in Guilin was where many Japanese tourists bought scrolls and procelain beads. There are souvenir shops everywhere-at the Great Wall, at Yangshuo at the end of the boat ride up the river Li, and at Shoshan, Chairman Mao's birthplace, where you can buy high quality Mao T-shirts and the ultimated tacky plastic souvenir plaque.

In Peking, the department stores were mobbed, largely with crowds from out of town doing their family shopping. Shelves were filled with folded clothes, accessories, cosmetics, household goods and fabrics. The big attractions were items brought to the Peking stores from other provinces, including many brightly colored synthetic blouses for women.

There is no greater store attraction, however, than a "long nose" foreigner trying on a Mao jacket ( $15 to $24 in synthetic blend, available in cotton for $8 but only with a ration coupon required for cotton-made clothes), or a Mao cap ( $1-red stars are sold separately for 10 cents) or a fake fur hat with turn-down earmuffs ($4.50 to $7). I found the crowd 100 percent friendly, commenting only when asked and willing to give a thumbs up or thumbs down on the purchase with a little encouragement. (Note: In department stores, the bigger the size, the higher the price tag.)

Store lighting starts with 40-watt bulbs-about the same wattage you will find as reading lights in most Chinese hotel rooms-and is not the best for shopping. Chinese are you will find the items you want in the men's department rather than the women's departments, even it the item is to be worn by a woman. The injection of "fashion" such as colors and flimsy fabrics make the more classic men's things far more desirable.

Synthetics cost more than natural fibers since they are scarcer and the Chinese think they are better. Synthetic gloves, for example, bought hastily in preparattion for a trip to the Great Wall on a snowy day, cost $8; cashmere gloves discovered the next day cost $3.

Certain items can be bought only at a specialty store. Huge, colorful posters saluting Chairmen Mao and Hua in endless settings and groupings are only in a poster store. Fifteen posters cost about $2. Also in the poster store are local scenic prints that are decorative and cheap. In Guilin six such posters cost $1.

A store in Peking featuring rubbings of building or tomb reliefs offered them in several sizes, in color as well as black and white, from $1 to $4. They have the added bonus of being a breeze to pack and weigh absolutely nothing. Even by the dozen.

The hot seller in the bookstore, one of the most popular places in most towns, is Nixon's memoirs in Chinese. It costs about $1 and only an abridged version is sold in Chinese.

The lights are far brighter, the sales help speak English, and no one follows you around in the Friendship stores, where many of the items available in general stores show up. If there is a few cents difference in price, the saving is still monumental. Hog bristle brushes cost $1.75, lined leather gloves$6, cashmere cardigans $28, cashmere mufflers $15.

But not everything that is in the stores for the Chinese shows up in the Friendship stores. Some of the handsome everyday dishes of the Chinese, for example, or cosmetic creams packaged in double shells, never surfaced in Friendship stores. And some things that are in one Friendship store do not show up in the next. A good rule is to buy things where you see them, even if it means the nuisance of carting them the rest of your trip.

No one will stop you from buying the way many Chinese do-from street vendors. No fancy folding tables a la Georgetown in Guilin, for example. Street vendors literally sell off the sidewalk. You bend over and join the crowd, many of whom will pull back when they see you. You can get streetside treatment of illness with herb ointments, have shoes repaired, and buy notions such as zippers, appliques, buttons and also food, all at prices slightly discounted from the general store price.

Prices are not to be haggled over. There is one price and it is set by the state.If you want the item, that's what you pay.

The legend was at one time that you couldn't use American Express checks, but whatever the problem was before it seems to have been cured. But don't expect to use charge cards. And only once did we witness private checks being accepted. In an antique store in Guangzhou (Canton), a psychiatrist from Los Angeles had lined up several antique porcelain vases he wanted to purchase. He gave the shop a check for $5,000. Once it cleared, he explained, the shop would ship him his order.

You don't have to go to the Peoples Republic to get the very best items from there. Of course, if you don't go you can't fully appreciate the history, the setting, or the skill with which these items are created.

But the fact is that there is a vast range of Chinese (PRC) goods availble in Hong Kong. And for the China traveler who puts off shopping for any reason, shopping is easier, assortments are often more varied and selections sometimes better in Hong Kong.

Let's start with the jade. Many jade experts feel the best items from China (PRC) have been skimmed off by the Hong Kong dealers. Chinese Arts and Crafts, with several Hong Kong stores, is the major arm of Peoples Republic export products. Obviously, you won't find one of everything you saw in China, but you will also find a lot of things you never came across on the mainland.

At Yua Wha, the China (PRC) department store in the Nation and Jordon Roads branch in Hong Kong, the assortment of laquered bamboo animals would make any department store envious Wood boxes with brass fitting cost $1 less than in Guilin, and a jacquarded silk jacket with silk wadding costs a couple of dollars more. But if you forget to get it the first time, paying a few bucks extra surely beats going home without it.

You can have clothes made in the Peoples Republic but you must work from what you already own and have with you. In the Friendship store in Peking, one of the alternatives was to choose a style from last year's Sears catalogue. In Hong Kong you can pick from the latest French and American fashion magazines.

The silks offered in the Peoples Republic are of unbeatable quality. The price is right, too.However, the colors and patterns-with few exceptions-are not very modern, if you happen to like current things. In Hong Kong, particularly at the Chinese Arts and Crafts (H.K.) Ltd., the assortment of fabrics, colors and prints would drive the home sewer bananas by the wealth of choice.

All good buys are not in stores or on street corners. All good item are not the touted jade and silks, clothes and accessories.The best way to shop in China is to keep your eyes open full-time and pick up items where you see them.

A good example from a recent visitors shopping list: panda-topped fountain pens, kiddie crayons two inches tall, a double happiness Ping Pong paddle, China Wall cigars, a small pencil sharpener decorated with a duck with a bobbing head, and a laundry bag with chinese writing and hotel room number bought from the hotel cashier. Everyone a winner. CAPTION: Picture 1, 2, 3 and 4, The Chinese symbol for market, and two ways to shop in Peking: the department store, top, and the Friendship store; photos by Nina S. Hyde; Picture 5, Sidewalk shopping in Guilin, by Nina S. Hyde-The Washington Post.