The scene: A telephone booth in a surburban New Jersey shopping centre. A foreign agent on a tricky mission is reporting to his superior.

"Such an unlikely location, Boris!Are you sure?"

Yes, chief. I've just located the caviar centre of the United States. It's hidden in a modest brick office building on the edge of a bourgeois neighborhood. I'm only about 20 miles from New York City. It's in a town called Englewood, but they use a Teaneck address. You have to search hard, but finally I spotted the name: Romanoff.

"Is he there? The master taster? The one we call Mr. Caviar?"

"Yes. his name is Arnold. He drives himself here each day from another suburb, across the Hudson River. He uses an American car, not even a Mercedes, and he follows different routes. Claims he's trying to beat the traffic. Family man. Tall, dresses consevatively. Polite modest."

"You've met him? You've been inside?"

"It was easy. You only have to mumble a code at the entry. 'MBT,' I said, and they let me in. They gave me a plastic spoon (obviously a capitalist trick) and let me taste the caviar. All I wanted. Transfer me to the Caspian or I'm going to defect!"

Mr. Caviar in the foregoing, never-to-be-produced drama, is played by Arnold Hansen-Sturm, the real-life, 39-year-old president of the Romanoff Caviar Company. Romanoff, whose offices and sales center were in Manhattan from the beginning of this century, moved to New Jersey two years ago.

The move was symbolic. The company still sells more fresh caviar than any other importer, and New York City's hotels and luxury restaurants are major clients. But Romanoff is actively marketing other forms of fish eggs, most from fish other than sturgeon, in supermarkets across the nation. Roe (fish eggs) from sturgeon is the only kind that can be called caviar without a descriptive word to indicate the kind of fish from which it came.

(Although the name suggests of royal connections, Romanoff is not of the Romanov family. It is a division of Riviana foods, which in turn belongs to Colgate-Palmolive. MBT, granulated bouillon, is a profitable sideline Romanoff developed just after World War II.)

Caviar, the company claims, is very nutritious. With 35 percent protein, it contains "all 47 known vitamins and nutrients." Still, people don't buy caviar for their health. They buy it for status and for taste. Fresh beluga, the most admired type, sells for as much as $225 a pound in Manhattan specialty stores.

Beluga however, is not only expensive, it is hard to find. The giant sturgeon from which it is taken is being pushed toward commercial extinction and Hansen-Sturm predicts there will be "almost none" of this fabled caviar on the market within a decade.

"The price of beluga doubled from 1976 to 1977," he explained, "but demand hasn't fallen off at all. We are able to sell all we can get our hands on. There are ecological problems in the Caspian (the sea bordered by the U.S.S.R. and Iran, which yields most of the world's annual 35 to 40 netric ton harvest of sturgeon roe). There has been tremendous industrialization on the Russian side. Water has been drawn off from rivers for irrigation, so the sea itself has been receding each year. The sturgeon have been over-fished. They are planting 2.5 to 3 million fingerlings a year now, but it takes 14 to 18 years for a beluga (sturgeon) to mature."

The mature beluga may measure 14 feet and weigh 3,000 pounds. The much smaller sevruga grows up more quickly and yields superb, if slightly smaller, eggs. A third type of sturgeon is osetra. Malossol, a term that often cause confusion, is not a type of sturgeon, nor a brand of caviar, instead, it means "lightly salted" a very desirable quality, as those who have tasted overly salted fish roe of any type can testify.

Caspian sturgeon are fished by both Russians and Iranians. The impression that Iranian caviar is superior to Russian may date from 1958, when Romanoff began importing the former under contract with the Shah. Today the firm's imports are split evenly between the two nations. Hansen-Sturm stands neutral on the question of quality with one exception - pressed caviar. This is a mass of partially crused eggs with a very distinct flavor. Not fashionable in this country, it is "a pet delicacy" in Russia. "There is no question the Russian is better," he said. "Maybe they never gave the Iranians the right salt."

According to Hansen-Sturm, the Russians once ran all the stations (processing plants) on both sides of the sea and taught the Iranians the knack of processing caviar. "It is like making wine," he said. "There is a caviar master or maker, whose judgment is critical."

The processor grades the caviar. They have a tendency to upgrade," Hansen-Sturm said matter-of-factly. He, in turn, may downgrade. Size and condition of the eggs are factors, but the degree of salting is critical in tion. Although a very rare golden caviar brings the highest prices of all, contrary to the presumption in certain strata of society, color is not a factor in quality. It's a "fallacy" to presume that caviar with gray tint is superior to that which is jet black.

Hansen-Sturm himself inspects each shipment, tasting almost daily at peak periods and at least once or twice a week. He sniffs and studies the appearance of the eggs, but "the palate is the ultimate judge." Only one other man at Romanoff, a Russian who has been with the firm 40 years, is allowed to exert quality control in Hansen-Sturm's absence.

Can tasting caviar become a chore? A bore? "Do I still like it?" Hansen-Sturm said, batting back a question as he broke into laughter. "I love it. I absolutely love it!" His oldest son loves caviar, too, he reports. He is not quite 7 years old.

Fresh caviar is very perishable, so it is flown here, another factor in its high cost. After inspection some of the original containers are sent to commercial clients: cruise ships, hotels, restaurants and caterers. There are tins of 14,7 and 4 pounds. Others are repacked in 4-, 2- and 1-ounce jars for retail sale. Only two women, both with long service, are used as "key" packers at the plant. Naturally security is "considerable."

According to Hansen-Sturm, tins of fresh caviar should be stored at 28 to 32 dgrees, and only for a brief time at home refrigerator temperature. They will keep two to three weeks in the tin, but once opened the roe should be eaten soon, as it deteriotrates quickly. If kept too long, the eggs may become soft, or mold will begin to form. White specks in a freshly opened tin are harmless, however. They are related to salt.

Caviar also may be vacuum-packed. This - the product one finds in supermarket - is not to be dismissed. Processing gives the roe a longer shelf-life (up to two years) and reduces the price ($30 to $35 for a 3 1/2-ounce jar). It robs the eggs of some of their sparkle and crunch, but for most palates the difference will not be so great as the difference in price. Tasting both together, however, there is a difference.

The only "rule" about eating caviar should be obvious. If it's the real thing let it be a soloist. Taste caviar in as big bites as allowed by your conscience - or by consideration of those who may be expecting to share it with you. Hansen-Strum warns against using salted crackers and recommends unsalted butter. He likes lemon juice (and vodka) with pressed caviar, but takes beluga abd sevruga an natural .

Onion and even sour cream are left for other roe - Icelandic lumpfish, whitefish and salmon. These fish eggs come in 2- and 4-ounce jars, which sell for less than $5.

The popularity of these lower-priced caviars has grown enormously. Romanoff is promoting them as "affordable" caviars and has produced a series of 12 recipe booklets to encourage their use.

On the horizon there looms yet another challenge. The Soviets are said to be on the verge of market testing an ersatz caviar. "It's possibel it will find its place," Hansen-Strum said. "We have the know-how to make one, too, but I don't think it will go."

He would rather talk about the possible revival of the American caviar industry.

Sturgeon are once again being caught, and caviar of good quality (though not the equal of the imported, he feels) is coming from the Columbia and Sacramento rivers on the West Coast.

Domestic caviar is a subject that has a romantic appeal to Hansen-Strum because of its importance in his family history. His great grandfather, Ferdinand Hansen, came to the United States about a century ago to buy caviar for export. There was a large supply of sturgeon along the East Coast and processing plants could be found in the Delaware River and on Long Island. At its peak, between 100,000 and 150,000 pounds of caviar was shipped to Europe yearly.

When the sturgeon disappeared, the exporter became an importer. The American branch of the Hansen firm began selling caviar from Russia to wealthy New Yorkers and took the name Romanoff. Although the industry in Russia was nationalized following the 1917 revolution, supplies continued to flow to the United States through a European subsidiary. Today, the caviar trade appears to be firmer than almost any other aspect of U.S.-Soviet relations. But Hansen-Sturm has to shop in capitalist countries for his "affordables."