The Story Behind World's Most Valuable $5 Million Rare Stamp Auction

From domestic side hustle to stamp collector extraordinaire, here’s William H. Gross’s remarkable stamp collection.

PUBLISHED MAR 12, 2024

Cover Image Source: A rare Inverted Jenny plate block worth nearly $3 million | Photo by Spencer Platt | Getty Images

In June, the Robert A. Siegel Auction Galleries in New York will host an auction featuring the most valuable U.S. postage stamp ever known. This particular stamp, dating back to 1868 and valued between $4 and $5 million, is a rare one-cent piece known as the "Z-grill," adorned with the likeness of Benjamin Franklin. Remarkably, only two of these stamps are known to exist.

NEW YORK - NOVEMBER 02: A rare 1-cent Z-grill stamp depicting Benjamin Franklin that was issued in 1868 and named because of an experimental security grill, is displayed before a swap for a block of four rare United States airmail error stamps, known as the Inverted Jenny plate block, worth nearly $3 million November 2, 2005 in New York City. Stamp dealer Charles Shreve, who is standing in for stamp dealer Bill Gross, swapped the block of United States airmail error stamps for a rare 1-cent Z-grill stamp. With the completion of the trade, the block's owner, bond investor Bill Gross, will own what is believed to be the first complete collection of 19th-century United States stamps ever assembled. The 1-cent Z-grill stamp is a blue stamp depicting Benjamin Franklin that was issued in 1868 and named because of an experimental security grill. (Photo by Spencer Platt/Getty Images) — A rare 1-cent Z-grill stamp depicting Benjamin Franklin issued in 1868 and named because of an experimental security grill | Photo by Spencer Platt | Getty Images

Part of William H. Gross' stamp collection, this exceptional item reflects Gross' stature as the founder of Pimco in the 1970s, often regarded as the bond king.

Estimated Value

The highest bid ever recorded for a U.S. postage stamp stands at $2 million, achieved by an "Inverted Jenny" sold at Siegel in November 2023. Should the anticipated sale of the Z-grill fall within its projected price range, it will surpass this previous record.

On June 14, the Z-grill stamp, and 100 other pieces from Gross's collection will be auctioned at the Lotte New York Palace Hotel. Additional items from his collection will follow the next day at the Collectors Club of New York.

The "Z-Grill" Stamp

The history of the "Z-grill" stamp is remarkable. Acquired by the New York Public Library through donation in 1925, it remains the only other surviving copy. Initially sold for $90,000 in 1977, Robert Zoellner acquired it for $418,000 in 1986, with Gross later purchasing it for $935,000 in 1998.

Siegel's explanation of the Z-grill's rarity traces back to the post-Civil War era when the U.S. Post Office implemented new measures to prevent stamp reuse, including the "grill" technique—a waffle-like pattern pressed into the paper to deter cancellation mark removal.

Understanding Stamp Rarity

Grills, characterized by their waffle-like patterns, were utilized on U.S. stamps for approximately five years beginning in 1867. These grills varied in size and shape, denoted by different letters. The Z-grill, however, stands out for its extreme rarity.

Only two one-cent stamps, two 15-cent stamps, and six ten-cent stamps featuring the Z-grill have been verified as genuine. Notably, all of them have been used and canceled, including the one to be auctioned by Gross.

Anticipation and Value

Charles Shreve, the director at Siegel and Gross's philatelic advisor for over thirty years, expressed, "The anticipation for this sale has been building for years." According to Shreve, stamp enthusiasts frequently inquire, "That's fantastic. What about the other pieces from Gross's collection?" This eagerness extends to singular stamps as well, exemplified by the Z-grill.

Furthermore, Shreve considers this auction as "the most significant rare stamp event in decades," confidently stating, "There's no question that the two-day auction will surpass any previous stamp sale in terms of revenue." It is projected that the collection will fetch between $15 million and $20 million.

William H. Gross' Collection

William H. Gross initiated the sale of his stamps internationally in 2007, followed by domestic sales starting in 2018. Despite expressing regret over parting with the Z-grill, Shreve asserts that the eventual buyer will possess a truly unique item. Gross himself acknowledged in 1998, when he acquired the Z-grill, that it essentially completed his collection, leading to a waning interest in further acquisitions.