‘Bond King’ Bill Gross sells rare ‘Z’ Grill stamp for $4.4M — most valuable in US

America’s most valuable postage stamp sold for nearly $4.4 million on Friday.

The 1868 one-cent “Z” Grill was sold as part of the collection owned by “Bond King” Bill Gross, who co-founded asset management firm Pacific Investment Management Co., otherwise known as PIMCO.

The winning bidder chose to remain anonymous.

It’s the first time the stamp has been sold in 26 years, and among stamp enthusiasts, it is considered the most coveted.

The “Z” Grill stamp completes the entire collection that includes one of every postage stamp issued by the US Postal Service since 1847.

The “Z” Grill stamp came in a custom-made “Z” Grill Louis Vuitton trunk, which holds the stamp in an acrylic frame.

“We call them Blue Chip Stamps,” said Scott Trepel, president of the Robert A. Siegel Auction Galleries, the auction house behind the sale.

“They’re not hard to understand. They’re very rare. And they fill a very basic need for a stamp collector, which is, ‘I’ve got to have this one if I’m going to complete my collection.’”

The 1868 one-cent “Z” Grill was sold as part of the collection owned by “Bond King” Bill Gross, who co-founded asset management firm Pacific Investment Management Co., otherwise known as PIMCO. MediaNews Group via Getty Images

The “Z” Grill stamp features Benjamin Franklin, and it’s one of the two of its kind that exist.

The other stamp is owned by the New York Public Library, currently on loan to the Washington Smithsonian National Postal Museum, and can never be sold.

“It’s the holy grail of collecting United States stamps,” Charles Shreve, director of the U.S. Siegel Auction Galleries and the philatelic adviser to Gross.

The “Z” Grill stamp completes the entire collection that includes one of every postage stamp issued by the US Postal Service since 1847. Siegel Auction Galleries

A grill is a mark that is impressed on a stamp to keep it from being reused.

The grilling stamp created a waffle-like embossment that releases an ink that would spread into the fibers and prevent it from being cleaned.

The “Z” Grill, named for its zigzag pattern, is considered the rarest of grill varieties and was used for a short period of time.

In addition to Gross, other famous people have owned this stamp, including Jerry Buss, once the majority owner of the Los Angeles Lakers.

For Gross, philately is steeped in his childhood after his mother bought stamps in the 1930s and 1940s in hopes they would pay for his college education.

The “Z” Grill stamp came in a custom-made “Z” Grill Louis Vuitton trunk, which holds the stamp in an acrylic frame. Siegel Auction Galleries

Gross’s interest in stamps served as not only an investment, but also a passion and an outlet for enjoyment and achievement.

“He likes to take chaos and turn it into something that is set, creating order out of disorder,” Shreve said.

“That has given him a sense of pride of accomplishing something.”

It’s why Gross would take calls from only two people during the day: “Warren Buffett and me,” Shreve told FOX Business.

“To have a break from the real world.”

Gross and Shreve would scan auction catalogs while watching football games and make purchases late at night.

“While stamps are used less and less these days, stamps are pieces of Americana, and people like to collect things that were in the past,” Shreve said.

“When mail was being sent in the 1860s, 70s, 80s, that was the internet.”

Gross obtained the “Z” Grill stamp in 2005 as the last step of completion for having every stamp needed in the collection, according to Shreve.

As his representative, Shreve bartered with the Mystic Stamp Company for a plate block of Inverted Jennys worth nearly $3 million.

It’s considered the “greatest stamp swap of all time.”

In the past few years, Gross has sold more than $50 million in stamp value.

Collecting stamps also makes for an alternative investment.

“Given the choice between putting money into the financial markets and getting an investment return or buying something tangible where you cash in your profits when you go to sell it, it’s a game,” Trepel told FOX Business.

“For some people, it’s art, and they buy art from artists who they think someday are going to be worth much more. In real estate, it’s location. In stamps and coins and collectibles, it’s generally the things that everybody wants or will want in the future.”