There's a wrong way to approach "The 1847s: America's First Stamps." Inspect it as you might any other show of 19th-century engravings and you'll miss its finickiness, the arcane lore it's soaked in, its competitive obsessions. True, it's full of pictures, and they're hanging on the walls of a Washington museum. But the museum is the National Postal Museum, and the pictures are on postage stamps, and that makes all the difference. "The 1847s" is less a print exhibit than a stamp collector's dream.

Stamp collecting is for some a mesmerizing pastime. I tried it as a kid. What I remember most is opening small packets of brightly colored postage stamps, most of them quite worthless, all sent me "on approval" by slightly seedy dealers who advertised to children in the back pages of comic books. The stamps seemed little windows opening to curiously named places far, far away.

Manchukuo . . . Andorra . . . Sao Tome and Principe . . .

And neat gear was required -- stamp tongs, glassine hinges, big intimidating albums never to be filled.

Stamp collecting is a little like print collecting (rarity in both is a determinant of price, small details loom large and dealers hold the high cards) but they are not the same. Art is supposed to be a way to the transcendent. Stamp collecting seemed more like crossword puzzles, or solitaire, or armchair exploration. It made the hours vanish. To fill in what was missing was one of its chief goals. And its byways were as narrow and as twisty as could be. And the whole thing was delicately tinged with imperialism: To own stamps was to own little pieces of the world.

But world collecting is kid stuff. No serious stamp collector is interested in all the stamps. Or even in all the American stamps. "The 1847s" deals with only two.

Benjamin Franklin, in sepia, appears on one, which cost a nickel. George Washington, in black and white, peers out of the other, which cost a dime. Or did when it was new.

For collectors of American postage stamps, 1847, the year both stamps were issued, is a year of high importance because it was the first.

No art collector can hope to own the first painting, or the first sculpture, but stamp collecting starts with exceptional precision. May 6, 1840. Before that famous day, stamps as we now know them didn't exist.

On May 6, 1840, at the instigation of one Roland Hill, a post office reformer, the government of Great Britain issued the Penny Black.

That first stamp (which shows the head of Queen Victoria, crowned, full-jawed and young) changed the mail. Many were the problems it resolved all at once.

Postage fees before that were dauntingly complex. How far would the letter go? How many sheets did it contain? How much did it weigh? The postmaster was expected to make the calculation, record it in his ledger, receive the sum involved, and then write "paid" upon the missive. The paperwork was stifling. Cheating was not unknown.

Now, for just a penny, a letter would be sent to any address in the kingdom. Now mailboxes were possible, and stamps could be accounted for. So great were the savings that the average cost for British letter-senders dropped by 89 percent.

The system in the United States, pre-stamp, was even more ramshackle. The distances were greater, the weather fiercer, the bridges shakier, the roads muddier. And postage cost a lot.

In the 1830s, shippers charged a dime to move a barrel of flour from New York City to Portland, Maine. To send a half-ounce letter cost 18 3/4 cents.

On June 10, 1840, only weeks after the issuance of the Penny Black, Sen. Daniel Webster urged America to follow suit. Two stamps, and two rates, were eventually agreed on: for half an ounce traveling less than 300 miles, five cents; for greater distances, 10 cents.

The stamps were printed by the New York firm of Rawdon, Wright, Hatch & Edson. They were first issued July 1, 1847. That's when the show begins.

Between 1847 and 1851 the Post Office distributed fewer than a million stamps a year.

This year the Postal Service will print nearly 50 billion.

These days you can buy your stamps in drugstores. In 1851 you could get them only at the post office. There were 20,000 post offices in the United States, but few had any stamps to sell in 1847. Only 5 percent of them received stamps from headquarters. And more than half the stamps were sent to four cities: Boston, New York, Philadelphia and Baltimore.

Do you care? Stamp collectors care. Where a stamp was purchased matters hugely to its price.

A single learned volume, a remarkable compilation, lies behind this show. It was written by Thomas J. Alexander, a philatelist of mind-boggling patience who is the exhibition's curator. His specialty is "covers," or envelopes that have been stamped, addressed and mailed. His catalogue describes -- in 949 close-packed pages -- all of the 1847 covers known to exist.

There are 12,961 of them. One hundred forty are displayed here.

Lots of collectors can afford an 1847 cover mailed in New York, but not many want them. They're too common. That's because New York was granted more than a quarter of the 5-cent Franklins and more than a third of the 10-cent Washingtons. Ah, but a cover from Minden, La., that's another matter. Only three are known. One is in the show. Philatelists know of only one 10-cent 1847 cover from Iowa. It's here, too. So is the only 1850 cover from Allegan Court House, Mich. And the only 1847 from Sing Sing prison in New York.

These days a common New York cover in pretty good condition might cost you $700. One with a much rarer marking and a block of four 1847s sold not long ago for $80,000.

If you want to see stamps that are cut in half, you can do so in this show.

Some notably handsome envelopes also are on view. Some are valentines prettily embellished with flowers. Some are "ladies" letters with delicate decorations. Some are somber mourning letters fringed in black.

But good looks don't much matter in this realm of collecting. An ugly stamp might cost a lot more than a pretty one. The coarseness of the image on the British Guiana 1-cent magenta doesn't matter. That small stamp with a sailing ship on it remains the collector's grail. Only one is known to exist.

King George V of England tried to buy it at auction in England in the 1920s, but was outbid by an American, Arthur Hind, who paid $32,500. In 1940, Hind's widow sold the rarity to collector Frederick T. Small for $40,000. Small owned it until 1970, when he sold it at auction for $280,000. Dealer Irwin Weinberg bought it, kept it for 10 years and then put it on the block again. This time it went to a du Pont for nearly $1 million. It would sell for much more now.

For collectors of American material, the 1867 1-cent embossed with a Z-grill pattern is the stamp most in demand. Philatelists know of two. One, in the New York Public Library, hasn't been seen in 30 years. The other was sold at auction in 1998. It fetched $935,000.

The 1847s weren't perforated. They were sent out in 100-stamp sheets, called panes, which had to be cut apart.

The mail is different now. Most is typed or printed. Much of it is junk. Romantic it is not. But once upon a time these small rectangles of paper glued to handmade envelopes helped to sew America together. And once upon a time our handwriting was better, a lot better. It flowed and swooped and swirled. The covers on display might fascinate a graphologist, but that's another realm.

The 1847s: America's First Stamps is on view through May at the Smithsonian Institution's National Postal Museum, 2 Massachusetts Ave. NE, just west of Union Station. Many of the objects are on loan from collector Guido Craveri, who paid for the exhibit. 10:30 a.m.-5:30 p.m. daily. Free.

Philately 101: America's first two postage stamps were printed on July 1, 1847. These early stamps are included in the National Postal Museum exhibition.This letter's 10-cent stamp was cut in half diagonally by a postmaster who ran out of 5-cent stamps. It is on display at the National Postal Museum.