Harry Truman dispatched Walter Mack to Haiti some 30 ago on an economic fact-finding mission. Mack returned to recommend that a soap factory be built on the island exploiting the coconuts that grow there.

Truman never acted on the recommendation, but Mack has slept soundly ever since, secure in the knowledge that his judgment was sound.

That confidence may explain why at the age of 83 Mack is bringing King Cola on the market to compete with the two reigning gaints in the field, Coke and Pepsi.

"I'm just an old cola person having a good time," he said yesterday amidst the fanfare he fomented to publicize the advent of King Cola in the Washington-Baltimore area.

His competition doesn't take him so lightly. For anyone who was in the cola business in 1938, the deja vu is considerable. It was then that Walter Mack founded Pepsi Cola and molded it into an international giant before stepping down as president in 1951.

"He's one shrewd old cookie," acknowledged Paul Polcan, area manager of Coca Cola's Silver Spring operation, who was on hand to gather intelligence on the enemy.

As far as the few hundred people who lined the intersection of 15th and L Streets around noon were concerned, though, Mack appeared to be one outrageous sugar daddy who gave away two mink coats to draw people out in the October chill to taste his new drink.

"Grab a Mink Coat," read ads which ran in two area newpapers hearalding his "mini parade." And that's exactly what countless women came to do.

"I'm here for my free mink," Erline Byrn said. "This is the only way I'll ever get one."

"I want to win one so I can sell it and trade it in for a down payment on a condominium," added Mary Lou Reilly.

In the tradition of P.T. Barnum, Mack had hired a band, outfitted in Elizabethan costumes, to ride a flatbed truck and distribute 1,500 ballons, each of which had a coupon inside worth a free six-pack of King Cola. Four of the balloons had coupons good for $100 worth of groceries, and two had coupons good for a mink coat.

"I'm going to need it if we stand out here much longer," said Harriet Williams, who shivered during her lunch break and waited for the parade, which was late.

When the truck, followed by an old fire engine with more Elizabethan types on it, arrived and threw out ballons, 15th street turned into a facsimile of a Hollywood game show. People almost trampled one another for a chance at the mink.

"Make the switchahola for King Cola," the band chanted over a wave of disco music as the rush went on.

Mack watched all of this calmly with Julian Nicholas, deputy director of the Office of Business and Economic Development, who officially welcomed Mack to Washington and who, it turned out, had gotten his first job out of college at Pepsi in the mid 50s.

"It's time someone came in and modernized this industry," Mack said, still dapper in a blue three-piece suit, wide-brimmed grey felt hat, and gold watch chain. "They all said, "how can you compete with them?' when I . . . took on Coca Cola in 1938."

Mack maintains that he will sell his cola 25 to 30 cents a six pack cheaper than his competitors because he will sell his product in bulk directly to wholesalers rather than distributing it to individual retailers as Coke and Pepsi do.

"Our overhead will be far less," he explained. "It will be like Campbell's Soup. It goes straight to the wholesalers."

Mack also will contract with established bottlers and canners rather than build expensive plants himself.He has divided the country into 29 "kingdoms" which, in plain English, are frachises. The Washington-Baltimore "kingdom," of which the King Cola company owns half, sold for some $1.2 million, according to King Cola President John Donlevy, who accompanied Mack yesterday.

Mack is reunited in his new venture with his old friend and colleague from Pepsi, Thomas Elmezzi, a relative youngster at 62. Elmezzi was Mack's chief chemist and the man who created the Pepsi formula.

Mack's competitors aren't worried yet. "If his service isn't any better than his parade, he's in a lot of trouble," Polcen said with a smile.

"This is the wrong time of year to introduce a soft drink, anyway," added Russell Wheeler, Polcen's marketing director.

These intricacies were lost largely on the crowd, who came out of curiosity and greed. Mink is still magic.

Linda Carr, a 33-year-old clerk-typist who works for the Army, was the stunned winner of one of the mink coats. She stood motionless as Mack graciously helped her into it. It didn't matter that she already had a raincoat on.

Taste remains a subjective thing. It would be wrong to read too much into the reaction of one man who, after tastig a can of King Cola, asked no one in particular, "Anyone got any whiskey?"