The United States’ 1868 one-cent Z grill stamp achieved a historic milestone by selling for $4,366,000 US (about $5.9 million) during the first day of Robert A. Siegel Auction Galleries’ June 14-15 sale of William H. Gross’ complete collection of classic U.S. stamps. This sale set a new record for a single U.S. stamp, underscoring […]