'Greatest collection' of U.S. stamps to be auctioned this weekend

Final auction of billionaire Bill Gross' collection expected to set record for sale of rare stamps

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Bill Gross became only the second person to own a complete U.S. stamp collection. (Credit: Getty Images)

Bill Gross watched as 11-year old Zachary Sundman outbid him (on behalf of Sundman's father) at $935,000 for the coveted one-cent Z-Grill postage stamp in a 1998 auction.

Gross would have to wait another seven years, but, finally, he was able to add the coveted Z-Grill to his collection via the “Greatest Stamp Swap in History," trading a 24-cent Inverted Jenny Plate Block he’d bought for $2.97 million in return for the final piece to his collection.

Gross was able to complete his collection via the “Greatest Stamp Swap in History." Here, Donald Sundman, left, seals the trade with stamp dealer Charles Shreve, who was standing in for Gross. (Credit: Getty Images)
Gross was able to complete his collection via the “Greatest Stamp Swap in History." Here, Donald Sundman, left, seals the trade with stamp dealer Charles Shreve, who was standing in for Gross. (Credit: Getty Images)

The trade allowed to Gross to reach the pinnacle of philately, aka stamp collecting: A complete collection.

In the world of philately, the ultimate goal is completion. For many, known in the industry as “album collectors,” that means filling every space in the album. Since collectors of the same categories have the same albums, that means some particularly rare stamps can ignite fierce competition.

But even for those with the deepest pockets, such as Gross, a billionaire who made a name for himself as the “bond king” and the co-founder of PIMCO, money can’t solve the basic fundamentals of supply. Just as Gross learned in the case of the Z-Grill auction, it can take years to track down the rarest stamps.

Gross, 79, is only the second person to compile a complete U.S. stamp collection — a feat made all the more impressive considering the title can only be held by one person at a time, since only two one-cent Z Grills exist, and one resides in the collection of the New York Public Library, which received the stamp as a donation in 1925.

“I call it the greatest game of keep away,” said Scott Trepel, president of Robert A. Siegel Auction Galleries. “It’s people who have the stamp who love to torment all the people who don’t.”

Gross told the New York Times in 2016 he had spent more than $100 million amassing his collection.

Gross donated $8 million to the National Postal Museum in 2009 to create a 12,000 square-foot gallery to house rare stamps from his own collection, as well as the National Stamp Collection, in addition to the creation of educational exhibits and public programming.

“Stamp collecting has been such a rewarding and educational hobby for me that I wanted to share the joys of philately in a way that would benefit future generations of students, citizens and scholars,” said Gross in a 2009 release. “The gallery at the Smithsonian’s National Postal Museum will use stamps and mail to offer a unique perspective on American history and identity. The story of stamps in America is the story of America, and I am proud to be part of preserving and showcasing these treasures.”

Trepel’s auction house will handle the sale of Gross’ complete collection of every Scott-listed postage stamp issued by the U.S. government this weekend, marking the fifth and final auction of the Gross collection — collectively dubbed the “greatest collection of United States philatelic items ever formed.”

The auction, which includes a plethora of unique and valuable stamps, should “establish a new record for a single U.S. stamp collection,” Trepel said.

Trepel, who has been involved in the industry for more than 40 years, has watched the development of the sports memorabilia market from afar, believes stamps are “more of an intellectual pursuit,” differentiating profit-motivated manufactured products such as sneakers and collectibles from stamps, which he says represents a more significant message.

“They’re a powerful image from the government,” Trepel said. "So you know, they still have that clout behind them. And we also have the post office as a marketing force. So, few collectibles have every post office in the country pitching their product”

Despite the shock to the supply of rare stamps poised to be injected into the market due to the sale, Trepel isn’t concerned there will be any negative effects caused by the abundance of offerings.

"I imagine it's going to be a battle of the generalists versus the specialists,” Trepel said. “So, there will be album collectors, they are going to want some of these stamps to fill their albums. But there are also going to be specialists who only collect one issue, one type of design one period, and so they will compete. And the interest comes from many different places, therefore the competition comes from different places.”

The collection is estimated to earn between $15 million and $20 million, highlighted by the famous Z-Grill, which will be available for public bidding for the first time in more than 25 years and holds an estimate between $4 million and $5 million.

Featuring the image of Ben Franklin, the one-cent Z-Grill is the most sought-after U.S. Postal stamp in the collecting world.
Featuring the image of Ben Franklin, the one-cent Z-Grill is the most sought-after U.S. Postal stamp in the collecting world.

Produced from 1867 to around 1870, the Z-Grill was specially produced to prevent stamp cleaning, or reuse, which the government feared would lose it money. Its zig-zag pattern imparted a mark onto envelopes that would act as evidence if one attempted to remove them for reuse.

One-cent Z-Grills soon emerged, alongside the philatelic hobby’s growth in the early 20th century, as the most coveted U.S. stamp in history. The first one-cent Z Grill was discovered and reported in “Collector’s Journal” in January 1915. A year later, the second and final example — which appears in the Gross collection, was identified, though did not resurface until 1957.

The Z-Grill’s sales history is extensively documented, a typical feature of the stamp collecting world, which seems to attract hyper-organized and detail-oriented hobbyists. The stamp has been sold four times (five if you include the famous trade), beginning in 1975 for $42,500, then two years later for $90,000, again in 1986 for $380,000 and in 1998 for $935,000 (when Gross lost the auction).

Gross told the Financial Times that his decision to sell off his collection was due to a belief that the market is headed for a correction, an odd comment for a seller to make publicly in the lead-up to an auction.

“It’s the strangest thing,” Trepel said of Gross’ remarks, citing the growth of the industry through online marketplaces such as eBay. “He has no data points to support the idea. I have no reason to be pessimistic about the future of stamp collecting.”

The current record holder for the most expensive U.S. stamp ever sold belongs to the Inverted Jenny, which sold for $2 million in 2023. The record for the most expensive stamp ever sold was set by the one-cent magenta from British Guiana, which sold for more than $8 million in 2021.

Will Stern is a reporter and editor for cllct.