"I came in with Halley's Comet in 1835," Mark Twain told his biographer Albert Bigelow Paine in 1909. "It is coming again next year, and I expect to go out with it." And so he did.

The combination of Twain's remarkable prescience, the 150th anniversary of his birth, the 100th anniversary of the publication of "The Adventures of Huckleberry Finn" in America and the return visit of the comet seems to have inspired the U.S. Postal Service.

Accordingly, in its final issue of the year, the United States is putting out an unusual double-header 36-cent aerogramme that commemorates the anniversaries, cites Twain's prediction and welcomes the comet. It is coming out this Wednesday in Hannibal, Mo., which was both Twain's boyhood home and the inspiration for his most notable writing.

In his talk with Paine, Twain went on to say, "It will be the greatest disappointment of my life if I don't go out with Halley's Comet. The Almighty has said, no doubt: 'Now here are these two unaccountable freaks; they came in together, they must go out together.' " The complete quotation, along with a tiny picture of Twain, is at the lower left of one fold of the aerogramme. At the upper right is the imprinted stamp showing a streaking comet with a flared tail. Stretching across over both elements in one line of black type is "1835: Mark Twain: 1910: Halley's Comet: 1985."

Mark Twain, the pen name of Samuel Langhorne Clemens, was born in the Missouri village named Florida and was 4 years old when his family moved to Hannibal. "It was a heavenly place for a boy," Twain recalled.

He drew extensively from personal experience in his writing and in his roles as a humorist and lecturer, which brought him great fame. He had no schooling after the age of 12. After his father's death, he was apprenticed to a printer's shop -- "the poor boy's college," Lincoln called it.

He then became a steamboat pilot on the Mississippi, a gold miner in the Far West and a reporter for a frontier newspaper, the Virginia City Enterprise. At 28, he met the humorist Artemus Ward, a master story teller who encouraged him to seek a wider audience. His humorous pieces met with success, as did appearances on the lecture platform, and Twain was on his way.

The significance of Halley's Comet is that it was the first comet for which a periodic pattern was established. In 1705 the English astronomer Edmund Halley noted similarities in the orbits of major comets that had appeared in 1531, 1607 and 1682. He determined that comets moved in elliptical orbits and postulated that the three sightings represented return visits of the same comet, which, if revolving about the sun approximately every 76 years, would reappear in 1758. It did, and then again in 1835 and 1910. The comet is currently center stage.

Collectors of first-day cancellations have alternative ways of acquiring the aerogramme, and a deadline of Jan. 3, 1986 -- orders must be postmarked by that date.

Collectors acquiring the aerogramme themselves should send it for servicing to Customer-Provided Stationery, Mark Twain-Halley's Comet Aerogramme, Postmaster, Hannibal, Mo. 63401-9991. All aerogrammes must be folded properly and addressed on the proper side. No remittance is required.

Collectors preferring full processing by the Postal Service should send 36 cents for each aerogramme with a first-day cancellation and send their orders to Mark Twain-Halley's Comet Aerogramme, Postmaster, Hannibal, Mo. 63401-9992.