[Berkley]

Some references on the distinction between "revolvers" and "pepperboxes":

The origin of the word "pepperbox" as applied to firearms is obscure. The nickname was more popularly adopted by the purchasers and users of these arms in the mid-19th century and came into wide popular acceptance by collectors of the 20th century, rather than being adopted by the gun manufacturers themselves. As attested to by advertising, instruction sheets and other literature of the era, the makers preferred to term their arms as "revolving pistols" or "repeating pistols."

-Norm Flayderman, Guide to Antique American Firearms, 8th Ed.

The brothers Benjamin and Barton Darling were granted a patent for the first American pepperbox.... Mr. Benjamin Darling has been repeatedly quoted as having maintained until his death at an advanced age that he invented the first American revolver. (The word "pepperbox" was not in vogue at the time of his invention, though it had been used earlier and was to be revived a few years later in America. In the 1830's a pepperbox was a "revolver" or a "rotary pistol.") The Darling patent, dated April 13, 1836, claimed the rotation of the cylinder by cocking the hammer; the Colt patent, which also claimed this mechanical rotation, was dated February 25, 1836 - some seven weeks earlier.

-Lewis Winant, Pepperbox Firearms

My brother...had a small-sized Colt's revolver strapped around him for protection against the Indians, and to guard against accidents he carried it uncapped. Mr. George Bemis was dismally formidable. George Bemis was our fellow-traveler. We had never seen him before. He wore in his belt an old original "Allen" revolver, such as irreverent people called a "pepper-box." Simply drawing the trigger back, cocked and fired the pistol. As the trigger came back, the hammer would begin to rise and the barrel to turn over, and presently down would drop the hammer, and away would speed the ball.

To aim along the turning barrel and hit the thing aimed at was a feat which was probably never done with an "Allen" in the world. But George's was a reliable weapon, nevertheless, because, as one of the stage-drivers afterward said, "If she didn't get what she went after, she would fetch something else." And so she did. She went after a deuce of spades nailed against a tree, once, and fetched a mule standing about thirty yards to the left of it. Bemis did not want the mule; but the owner came out with a double-barreled shotgun and persuaded him to buy it, anyhow.

It was a cheerful weapon--the "Allen." Sometimes all its six barrels would go off at once, and then there was no safe place in all the region round about, but behind it.

-Mark Twain - Roughing It, which follows the travels of young Mark Twain through the Wild West during the years 1861–1867.