‘Bond King’ Bill Gross Is Selling His Stamp Collection, With One Expected to Fetch up to $5 Million

A one-cent postage stamp from 1868 is expected to become the most expensive U.S. stamp ever sold when it heads to auction in June.

Known as the “Z-grill,” the stamp is the most-valued piece of what some industry observers have called the most complete and significant collection of American postage stamps ever assembled, one that was built over decades by a man nicknamed the “Bond King.”