Billionaire ‘Bond King’ Bill Gross Is Set to Sell a Record-Breaking $5M Stamp

The "Z-grill" stamp is expected to set a record for the most valuable U.S. postage stamp when it heads to auction this June.

Small blue stamp with perforated edges
A rare 1868 1-cent “Z” grill stamp. Courtesy Siegel Auctions

As a child, billionaire investor Bill Gross received a set of stamps from his mother, who believed the album could pay for his college. The stamps turned out to be worthless, but Gross—determined to prove to his mother that postage could be a good investment—went on to build one of the most significant U.S. philatelic collections ever assembled.

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Gross has sold international postage stamps for decades now, often gifting the proceeds to charity. But he’s saved the best for last. Filled with rarities like the erroneously printed Inverted Jenny and the historic Alexandria postmaster’s provisional, his collection of American stamps will hit the auction block this summer with a total estimate of between $15 million and $20 million. “This is, without a question, the most significant and most valuable collection of United States stamps formed this past half century,” said Charles Shreve, Gross’ longtime philatelic advisor, in a statement.

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Leading the upcoming sale at New York’s Robert A. Siegel Auction Galleries is a 1-cent “Z-grill” stamp from 1868, a rarity in postage collecting that is expected to become the most valuable American stamp when it fetches between $4 million and $5 million. It will likely surpass the current U.S. stamp record established at Siegel Auctions in November with the $2 million sale of an Inverted Jenny, although the global stamp record remains at $9.5 million after the 2014 sale of a 1-cent magenta stamp from British Guiana.

Why is the Z-grill stamp so valuable?

The Z-grill stamp might not have ever come to fruition were it not for concerns in the 19th century that the U.S. Post Office would lose revenue due to people cleaning off postmarks and reusing stamps. To allow cancellation ink to seep into a stamp permanently, innovations such as the “grill,” a waffle-pattern embossing, were applied to U.S. postage stamps between 1867 and 1872, with each design given a different corresponding letter. “In the case of Z grills, they look different because they were made from one particular grilling device that was unlike the others,” said Scott Trepel, president of Siegel Auctions, in a statement.

Of the two existing 1-cent Z-grills, one has been held by the New York Public Library for nearly a century. That leaves only available to collectors, and only a single philatelist can have a complete collection of all U.S. stamps at any given time.

Gross, who co-founded investment firm PIMCO in 1971 and has an estimated net worth of $1.6 billion, was determined to become that collector. Despite taking part in a 1998 Siegel sale offering up the stamp, he was outbid by dealer Don Sundman’s Mystic Stamp Company, which paid $935,000 for the rare stamp. But in 2005, he managed to trade a block of Inverted Jennies valued at nearly $3 million for the rare postage in a deal with Sundman known as the “greatest stamp swap of all time,” according to Siegel Auctions.

The Z-grill has been in Gross’ possession ever since. Having focused on philanthropic endeavors since retiring in 2017, the billionaire has given millions to institutions and groups like the National Postal Museum, Doctors Without Borders and the University of California, Irvine. His contributions are often funded by stamp auctions—his sales at Siegel Auctions alone have raised $24 million for various charities. It is yet to be announced whether this will be the case for the Z-grill, as no decision has been made regarding the disbursement of its sale proceeds, according to the auction house.

The rare stamp will be sold alongside 100 other lots on June 14, followed by the auction of Gross’s U.S. collection the following day. “For collectors who have patiently waited for this to happen, it is an opportunity to buy what they wanted for a very long time,” said Trepel. “And for others who just want one stamp—the rarest of the rare, the best of the best—it could well be an opportunity to capture a trophy.”

Billionaire ‘Bond King’ Bill Gross Is Set to Sell a Record-Breaking $5M Stamp