The 31-year-old son of billionaire “Bond King” Bill Gross has sold five rare postage stamps against his father’s wishes — and bagged nearly $1.9 million in the process.

The final gavel price for the prized “Inverted Jenny” stamps, however, fell sorely short of the $3.4 million hoped for by Nick Gross, an LA-based rock drummer — and he might have his pop to blame for the missing $1.5 million, sources said.



As The Post reported earlier this week, the elder Gross — who Forbes estimates is now worth $1.5 billion, even after a headline-grabbing 2016 divorce from Nick’s mother cost him $1 billion — has been fuming over Friday’s auction because he claims his son had no right to sell the stamps.

Gross claims he gave each of his three kids some priceless “Jennys” seven years ago — but on the condition his grandchildren ultimately inherit them, sources told The Post.

Earlier this week, lawyers for Gross wrote to the auction house, Spink & Sons, challenging his son’s right to sell the rare stamps. The bond-trading tycoon had even been weighing whether to bid on them himself, insiders said. But source close to Gross denied on Friday that the “Bond King” was a bidder.

“He’s decided not to pursue this any further at this time,” the source said. “He’s not going to make a capital case out of it.”

Gross’s letter to the auction house wasn’t a formal cease-and-desist order, so auctioneers moved forward with the sale as planned.

Nevertheless, the letter may have been enough to scare away bidders, insiders said.

“The low price could be a function of the dispute over ownership, over questions about title,” according to a source close to the situation.

A block of four of the prized “Inverted Jenny” stamps — named for a 1918 printing error that pictured a so-called Jenny biplane upside-down — ended up selling for $1.45 million.

That’s well short of the $2 million to $3 million estimate given by Spink & Sons, the auction house that sold them Friday afternoon.

The fifth stamp sold for $425,000, within the auction house’s range of $250,000 to $675,000.

Leading up to the auction, Nick, a drummer for the MTV-featured rock band Open Air Stereo, disputed that his dad put any restrictions on the stamps’ sale.

“If he would like to have the stamps back, he is welcome to buy them at auction,” Nick told The Post earlier this week.

In the end, Gross may have ended up pooping his son’s payday, said New York-based lawyer Jason Advocate.

“No buyer wants to be bogged down in a legal battle with a billionaire after the sale,” Advocate said, noting that the elder Gross “has unlimited resources to bankroll litigation and has a personal and emotional investment in the property.”

The father and son have been estranged since Sue — Nick’s mother and Bill’s second wife — filed for divorce three years ago after more than three decades of marriage.

The breakup was overflowing with court-documented hijinks, including Sue accusing Bill of stinking up her house by sticking dead fish in its air vents — and Sue admitting she forged a Picasso the couple once shared so she could keep the original for herself.

Nick has been so at odds with his dad that he refused to invite the one-time Wall Street icon to his wedding in July 2018.

Additional reporting by Kevin Dugan