ATLANTA (AP) _ A nationwide ''sting'' operation run by the U.S. Postal Service to snare buyers of child pornography has yielded indictments of at least 74 people, a postal official said.

More indictments are expected from Project Looking Glass, said Don Davis, manager of the Postal Service's Fraud and Prohibited Mailing Branch, in today's editions of The Atlanta Constitution.

Using material confiscated in previous raids, officials created a dummy corporation, the ''Far Eastern Trading Co. in Hong Kong,'' and sent out a mail-order catalog offering magazines, videocassettes and Super-8 films of 10- year-old boys and girls in homosexual and heterosexual acts.

Some customers, Davis said, insisted on getting their money's worth.

''One man placed an order, but he didn't get his magazines right away because we were behind filling them all,'' Davis said.

''So he wrote a letter complaining to the Postal Service that he had been ripped off by a shoddy mail-order company. He enclosed a copy of his money order.

''So we filled his order - and arrested him. We like satisfied customers,'' he said.

Investigators had to make copies of the videocassettes and magazines to have enough material for the operation, Davis said. Most of it was originally produced in Europe.

The operation, and the 74 sealed indictments, were to be announced today in Washington by U.S. Attorney General Edwin Meese, Davis said.

The customers have been charged with knowingly receiving child pornography through the mail, investigators said. A first conviction carries a possible prison term of up to 10 years and a fine of up to $100,000.

Davis said the customers were not entrapped.

''We identified people who had a predisposition to send or receive pornography through the mails,'' Davis said. ''We sent the catalogs only to people whose names we found on two different mailing lists seized in previous cases.''