On a wall in an office in midtown Manhattan: a letter from Lord Byron, in a fine, spidery, illegible hand; the signature, but just the signature, of Will Rogers; a typewritten thank-you note from Betty Grable, signed in red ink beside a cheesecake Christmas pose adorably mounted in green and red.

On the sofa, portly and irascible, the grand king of the handwriting business, the world renowned expert, Charles Hamilton. The man who coined the term philography, meaning love of writing.

A supplicant approaches, two autographed photos of John Barrymore in his outstretched hand. "Sincere good wishes," someone has written beneath the famous profile. The world-famous philographist assesses them before they are quite out of the envelope, without bestirring himself from the couch.

"That ain't his handwriting!" he says, in a voice undiluted by the niceties of etiquette.

The man demurs, offering a bit of info to show he's no callow neophyte off the street.

"Well, I knew he would have had to have written it before breakfast, 'cause after then he'd be sloshed," the man says.

"No, his handwriting looked like printing, even when he was crocked to the gunnels," says Hamilton. "Another thing he liked to do--rebus letters, when you put a picture in place of a word. It's a beautiful picture of him, though," he says picking up the photo. "Curse his black soul for not signing it."

Some in the profession sneer at Charles Hamilton, saying it is odious to auction off the autographs of Charles Manson and Son of Sam. But what arcane treasures he stores in his head! The place that Lord Byron is buried and also the epitaph for his dog! The precursors of Tennyson's "Idylls of the King," stretching back from Malory's "Morte d'Arthur" to the Chronicles of Nennius. The sexual proclivities of Hitler's generals as well as the more recent secrets of the stars.

Hitler, however, does figure into Hamilton's passions, his expert opinion (he has written l4 volumes, popular and otherwise) having been sought on the ersatz Hitler diaries by Newsweek and Life. Newsweek, for his money, came to him too late.

"They had already . . . consulted a guy named Ken Rendell," he says. "Now, Rendell is not an authority on Hitler. Rendell had asked me months ago if he could borrow a copy of Hitler's handwriting so he could look at it--you must read the issue to understand the humor of it--he said he'd have to ultraviolet-ray the original and look at it under strong magnification. This for a forgery, so help me God, that if the wind was right you could smell it in Zurich where they had it in a safe."

(Answers Rendell, a Boston-based dealer in rare manuscripts: "My God, that statement is ridiculous. We sell a significant number of Hitler letters and documents and I certainly know his handwriting as well as Charles Hamilton . . . I had borrowed a document from him on Hitler, but it's a ridiculous point . . . in this business we all borrow from one another . . .")

You could not call Charles Hamilton shy. His use of language goes beyond formidable, veering towards the belligerent: If anyone is found bludgeoned to death by the brutal force of words, the police would do well to stop by the Hamilton Galleries on 57th Street and pick up Charles. His language is peppered with insults; the voice cuts not like a knife, but ragged-edged, like a saw; the words "I told" run through his conversation like the refrain to a drinking song. Ask him a question he does not want to answer and he'll insult you and threaten to terminate the interview. Minutes later, in newly applied cologne, he'll come over to be sniffed and kissed. He has also donned his suit jacket for the photographer.

"The moment I put on a necktie and jacket you're gonna find that I am impeccably polite," he says mockingly but, of course, he's not.

Nor does he sit idly by as a reporter begins examining the letters from Einstein and Freud on the wall.

"Never mind looking at that crap," he says. "Don't you want to talk to me? I'll tell you some inside dope about the Hitler diaries . . ."

Barely is this out of his mouth before he's off and running. He embraces his story with gusto--giving the distinct impression he's told it before.

How did he know the diaries were forged? "Because I'm an authority on Hitler. I've written a two-volume work on autographs of the Third Reich. It contains 700 rather lengthy biographies, the most exhaustive study of Nazi leaders ever done, it contains 64 pages on Hitler's handwriting, and I am familiar with the comments by his various aides and adjuncts and servants and secretaries, and he kept no diaries, otherwise I would have known about it.

"Let me go a little further and say Hitler was not the kind of man to keep a diary. He would never put anything in writing if he could possibly avoid it, and certainly he would not put his intimate thoughts in writing because he was a very much withdrawn man, a very private man, very much like Howard Hughes in that respect . . ."

To Hamilton's charge that the Newsweek cover story had been written before the Newsweek reporter contacted him, Editor Maynard Parker responds that it is "absolute rubbish and untrue." The magazine, he said, "had not written a word" of the story at the time its reporter went to see Charles Hamilton. Explaining why Newsweek made the diaries its cover story, Parker said, "It was an interesting news story, a story of major historical interest . . ." The Newsweek story included a paragraph quoting Hamilton.

You may gather from this that Charles Hamilton is controversial. This would be an understatement. In the genteel and scholarly world of collectible manuscripts, where dealers would rather turn the other cheek than Go On The Record, he is the Bad Boy Without Equal. "I loathe the man," said one of the major acquisition men in the country, under the umbrella of anonymity.

On the record, where the general consensus is that Charles Hamilton is quite expert at authenticating material, the following is also said:

* That Charles Hamilton claimed the Howard Hughes will naming Melvin Dummar as a beneficiary was genuine, although a jury later rejected it as a fraud. (Hamilton, while saying cheerfully that he's probably made "a million errors," denied that the Hughes will was one of them. ("That will was never condemned as not being genuine," he insisted.)

* That Charles Hamilton, this from Massachusetts autograph dealer Paul Richards, is "very good when he takes the time and sits down and studies something, but sometimes he tends to be hasty."

"When Harry Truman's health began to fail, he went from using a stylus pen to using a ballpoint pen, which he had never used before," says Richards. "Hamilton immediately pronounced them the signatures forgeries because they were not characteristic. I knew Truman and I sent him a little something that had appeared somewhere quoting Mr. Hamilton and he wrote back that I was absolutely right, that he always signed his own mail." Hamilton has no memory of the Truman incident.

* That Charles Hamilton, according to colleagues in his field, by dealing in such as the letters of David Berkowitz, the notorious New York City sniper Son of Sam, and John Hinckley Jr., has dealt the rare books field a dirty blow.

"Even the best of auction houses sometimes offer items that could be described as bizarre, perverse, or merely tasteless . . ." wrote Art and Auction Magazine last November. "For sheer on-the-block yech, however, no one can beat Charles Hamilton, of the eponymous New York auction house specializing in autographs, manuscript, and varied memorabilia . . ."

Nonetheless, says Art and Auction editor Isolde McNicholl, "He is a jolly good businessman, he runs an efficient operation . . . he was one of the first people to say he thought the Hitler diaries looked funny . . . and he certainly does not have a reputation for selling things that are not what they say they are, no matter how disgusting they are . . ."

Another member of the rare manuscript community, John H. Jenkins, president emeritus of the Antiquarian Booksellers Association of America, pulls no punches about his feelings for Hamilton in a letter to a reporter prompted by Rendell.

"Mr. Rendell is the world's leading expert in autographs, which Mr. Hamilton is not," Jenkins begins. "Mr. Rendell is a past president of the Manuscript Society, which Mr. Hamilton is not . . . Mr. Rendell is the world's leading expert and author in the field of forgery detection, which Mr. Hamilton is not, although Mr. Hamilton wrote a book for popular consumption about forgers (not forgery detection)."

Ken Rendell, the object of so much of Hamilton's venom on the Hitler diaries, echoes the feeling that Hamilton, generally, is correct. "Ninety-five percent of the time, he's right," Rendell says. "But that other 5 percent of the time he shoots off his mouth" without doing enough research.

Clearly, the Hitler affair is not the only controversy that has surrounded the 69-year-old Hamilton, who has gone through his professional life with the critics buzzing about him like a dog who's been home to generations of grateful fleas. His professional life, after all, is heady. On a typical day, he may be approached not only by a stranger to authenticate a single letter, but by a wealthy family, asking him to assess a collection, or a relative of some departed eminence, wondering what this or that stack of old letters would fetch at a Hamilton auction. He determines authenticity based on historical data as well as his 30 years of familiarity with the material, and when he smells a forgery he becomes incensed.

He has fought with presidents--three administrations, he claims--over the use of autopens, those miserable replicating robots that send a message to philography dealers that there's no dough to be made here. He has sent a number of manuscript thieves and forgers to prison, and challenged the FBI on its authority to, say, retrieve a letter from Jackie Onassis to Lady Bird Johnson that had come into his hands. He dealt with the FBI, he says chuckling, by telling them they could pick up the letter the next morning. By the next morning he had notified the press. "Are you the messenger boys for the First Lady?" he asked the government agents. The FBI men reportedly hid their faces, but he did not. Wire service pictures show him with letter in hand. "Gestapo" tactics, is how Hamilton has characterized the FBI actions.

Does it surprise anyone, that in his youth, he was also a Bad Boy? Hid a dead cat under the schoolhouse, in Flint, Mich.; rubbed the radiator with limburger cheese before class.

He resists talking about his childhood, would rather slap a copy of Current Biography on the desk and relive past and present feuds ("I am not a parrot," he rails, "Do not ask me to repeat, that is one defect I do not have! Okay, you want to know my favorite color . . .?"). At length, however, for there are ancient battles as well, he gets into it: the teacher who punished him wrongly; another who was an ignorant fool. College was at UCLA, where he claims to have been the first student in the history of the English Department to complete all the work for a master's degree in one year.

Professional life was less successful: He worked in advertising, as an office manager, before, at age 39, he made the hobby of autograph dealing a profession. He had begun the hobby with the signature of Rudyard Kipling that he acquired when he was 12. He had admired Kipling, he says, "and the signature brought me very close to him . . . I touched the same thing he had touched. I've always been a hero worshiper."

He turned his first profit with a letter written by John Brown, purchased for $1, which brought $50; he was able to make a sweet profit on another letter because he was aware, with his odd bits of arcane knowledge, that a reference to "the old statehouse" was indeed a reference to Independence Hall in Philadelphia. That success brought others: a note in which Queen Isabella refers to the jewels she sold to bankroll Columbus; unpublished sections of "Walden" in Thoreau's hand. It has given him the knowledge that a diary allegedly written by Hitler on lined paper would not belong to Hitler, because Hitler used only the finest paper, gold embossed.

Success has given him, as well, a privileged view of the private lives of the famous; for what can be more revealing than a letter one writes to an intimate friend, never believing it will be peddled to the public from an auctioneer's stand. Hamilton claims not to be a collector, but there are certain treasures he keeps: a particularly revealing photo of Marilyn Monroe; a letter from the notoriously randy Errol Flynn. "My ----- was like a geiger counter, looking for women everywhere I went," recites Hamilton, from memory.

Other letters, to be assessed--not offered for auction--come his way as well. The parents of John F. Kennedy came to see him once, on such a mission, says Hamilton. So did Kennedy's late friend, LeMoyne K. Billings, who "in spite of my advice and even my pleadings destroyed many of the letters because of four-letter words, because he felt they would not reflect well historically . . . I hate to see letters like that destroyed, it genuinely hurts me . . ."

And did he pick up any new information on Kennedy, by the way?

He erupts.

"I'm not gonna tell you! Don't mistake me for Maxine Cheshire former Washington Post columnist , she is a dirt digger, I am not!" he hollers.

He had a problem once with Cheshire, winner of several journalism awards for her investigative reporting. It was l3 years ago, over some letters.

"You want to know how I broke with Maxine Cheshire?" he asks.

"Nope" doesn't deter him.

"But it's interesting!" he says. Double "Nope" has no impact.

"Dammit, this interview is not going any place as far as I'm concerned, I may terminate it at any moment!" he yells.

But he does not.