A wealthy investor has sold two of his prized stamp collections to help pay for an expansion of the Smithsonian's National Postal Museum.
William H. Gross sold the collections last week at an auction in New York. The collections included stamps from the Confederacy and British colonies in North America. They fetched $3.2 million.
The proceeds go toward Gross' $8 million pledge to the museum. He has also donated some of the rarest known stamps from his personal collection.
The museum's expansion from a basement space near Washington's Union Station is scheduled to open in late 2012. A gallery will be named in Gross' honor.