Ralph Delligatti usually can be found supervising the baccarat tables at the Dunes Hotel in Las Vegas, where he's a shift boss. But yesterday he was just another low roller at the Sotheby Park Bernet art auction house here, where historic pieces of paper were being fought for and won at prices up to $195,000.

"I made a few bids but the prices went way over what I expected," said Delligatti after the morning session. He still had his eye on a rare letter from President Zachary Taylor being offered that afternoon, but the way things were going, he was pessimistic. The letter's value was estimated at $750 to $1,000. "I'm willing to bid $2,500 for it and I bet I don't get it," he said. "I wouldn't be surprised if it brings over $4,000." The letter brought only $3,250.

But Sotheby Parke Bernet was quite happy anyway. It had billed the event as nothing less than the most important auction ever of "American historical autographed material" and had estimated that total sales would go as high as $800,000. Instead, they were $1,423,925. A record, said Sotheby Parke Bernet.

The autograph collection had belonged to Philip D. Sang, a Chicago ice cream and wholesale drugs tycoon (and "a remarkably warm and engaging human being," according to the sales catalogue). He died in 1975. The part auctioned off yesterday included 325 treasures of Americana, letters and documents signed by Washington, Jefferson, Lincoln, Grant, Kennedy, Davey Crockett, Nathan Hale, Jefferson Davis, King George III, Cortes, Talleyrand, Cotton Mather, Lafayette, Thomas Edison, Benedict Arnold and William Henry Harrison.

Antique-autograph collecting is something like stamp collecting, only more interesting because you get the whole letter instead of just the stamp.

Some of the letters sold yesterday made for fascinating reading.

There was a bill from Paul Revere to the Committee of Correspondence in Massachusetts for expenses incurred during his ride to New York to give the Sons o Liberty the word about the Boston Tea Party. Among "my Expences" was the sum of four pounds, 16 shillings to rent a horse. Beneath Revere's signature is an approval for the payment signed by America's best-known signer, John Hancock.

There were several documents concerning Maj. John Andre, the British officer hanged for spying in the Benedict Arnold treason case. One, which sold for $11,000, was a one-sentence note from a Continental Army officer to the jailed Andre giving him the worst new of his life; "Sr., His Excellency Genl. Washington has fixed the Hour at 12 o'Clock this day."

There was a letter from John Wilkes Booth describing a journey of incredible ill luck during which, in the space of one paragraph, he gets a frostbitten ear, loses his "treasured flask" and sees a wagon crush his best friend.

There was a 1777 letter to the Continental Congress from Gen. Lachian McIntosh, which blamed the recent death of a signer of the Declaration of independence, Button Gwinette, on the "unskillfulness of his doctor." The fact that McIntosh had shot Gwinette in a duel is brushed off as a minor factor in the man's demise though the general does admit being "partly the unfortunate tho' innocent instrument of it."

The Revere letter was the hit of the auction. It was bought for $70,000 by Malcolm S. Forbes Jr., son of the publisher of Forbes magazine. But the highest sale price was $195,000 paid for a packet of more than 50 letters and documents with the signatures of all the signers of the Declaration of Independence. These were bought by a dealer from a small town near Philadelphia.

Auctioneer John Marion sat in a pulpit-like wooden auction beer's bench with an overhanging canopy and chanted the prices as the hundreds of well-dressed bidders (and bidder watchers) raised their hands and assistants relayed their signals. Down it goes at $4,000," he would cry on a sale and give the desk a sharp rap with his gavel.

Delligatti had to be content with merely looking at such delight. "I came here not because I expected to get anything, but to examine the documents," he said. "It was worth the fare to me."

Delligatti said that most of the big bidders were book-and-document dealers, who only buy if they see a good investment. "I've been in land and stocks and I've never seen anything where you can invest and turn over quickly for profit like you can with this," he said.

But Delligatti isn't it for that. He's a collector. He started about 12 years ago, collecting autographs of show-business and sports figures, most of whom he met in Vegas. Elvis Presley started him off with two signed portraits of himself. But then one day Deligatti saw a catalogue advertising letters signed by U.S. presidents, something he hadn't known was available.

"I dropped all the show-business stuff when I realized that somebody like me could own a letter of a president," he said. He began with a signed picture for President Esienhower he bought for $30. He now specializes in presidents, the Civil War and the space program. One of his treasures is a 1930s letter from Charles Lindbergh to the pioneer rocket scientist, Robert Goddard, discussing the military potential of rocketry. He paid $800 for it. It's an expensive hobby. "I don't buy pieces that often," he said.

One of Delligatti's more successful compeitors was Michael Ginsberg of Massachusetts, a rare-book and manuscript consultant who was acting as an agent for the Jenkins Co., a huge book store in Austin, Tex. Ginsberg, who went rushing for a phone to report his results to Texas as soon as the morning session ended, wasn't even sure how much he'd spent. "I bought seven or eight things," he said."After a while it's difficult to keep track of the numbers."

One buy he remembered quite well, however, was a circa-1540 letter from Hernan Cortes, the Spansih conquerer of Mexico. Ginsberg's winning bid wqs $20,000. "We are prepared to go twice as high," he said. Why"Cortes is probably the rarest of all South American autographs. There hasn't been a Cortes autograph for sale for maybe 65,70 years."

It was Ginsberg who made off with the Zachary Taylor letterthat Delligatti had fancied. You can't beat the pros.