One of the least publicized but most influential auction companies in the area is Earl P.L. Apfelbaum Inc. Since 1930, it has specialized in stamps, for years in a Center City salesroom with space for only a few dozen bidders.

The salesroom's size was immaterial since the auctions involved some of the world's rarest and costliest stamps and attracted absentee bidders from far and wide.

On Tuesday at its current location in Jenkintown, Apfelbaum will be selling a specimen of what is sometimes called the most famous stamp of all: the inverted Jenny. The 1918 24-cent carmine-and-rose airmail depicts at its center a biplane that was printed upside down.

The stamp is one of just over 90 that exist today out of the original 100 printed before the error was spotted, according to company president John Apfelbaum. One authority puts its value at $400,000.

It is part of a single-owner collection of all the inverted-center stamps of the United States. Along with three inverts dating to 1869 and four to 1901, the collection has one, whose value is put at $26,000, that was printed in 1992 to celebrate the bicentennial of the New York Stock Exchange.

Book values are included in the catalog descriptions of all 218 lots in the sale, which begins at 1 p.m. in Suite 831 of the Pavilion, 261 Old York Rd. Most bidding will be done in advance online or through other absentee methods.

Book-value listings notwithstanding, Apfelbaum described the sale as "unreserved" - that is, no minimum bids. "Those prices are Scott Catalog values," Apfelbaum said this week, referring to the well-known philatelic publisher.

(Book values for many collectibles tend to the high side because they are sometimes used as replacement prices in insurance claims.)

Although the auction catalog lists the $400,000 Scott appraisal for the inverted Jenny, the actual sale price may be far different. So far, Apfelbaum said, the high bid for the stamp is $150,000, although "one very similar in appearance but slightly better sold in New York City last month for $977,000," he said.

Other top lots and their book value include a 1906-08 four-cent U.S. Grant "imperfect" ($75,000), an 1857-61 five-cent brick-red depiction of Jefferson, and an 1869 30-cent ultramarine-and-carmine stamp with flags inverted (both $80,000).

Because of the extraordinary collection, Apfelbaum expects a larger-than-usual number of bidders "in the chairs" at Tuesday's sale, perhaps 12 to 15. "The major buyers want to come to the sale themselves or send an agent."

Usually, though, most winning bids are absentee, even more so than in the days when Apfelbaum's was located on Walnut Street. "Half our sales go to Internet bidders," he said, with mail and telephone bids also common.

To bid online, go to

or e-mail bids to

» READ MORE: Bids@apfelbauminc.com

For more information, call 215-567-5200 or 800-523-4648.

Contact David Iams at daiams@comcast.net.