In a record-setting one-day stamp auction that raised sales of $9.1 million, billionaire bond fund manager Bill Gross unloaded a series of early British stamps featuring a young Queen Victoria. The proceeds raised were donated as one sum to Doctors Without Borders; it was the medical organization's largest donation ever received in its 36-year history.

The top lot auctioned Monday morning included two items. The first was described as "the largest surviving mint Penny Black multiple still in private hands," consisting of 18 stamps, coupled with a strip of six stamps that were separated from the larger bunch. The two pieces together were ultimately sold for $1 million to an unnamed bidder. Attending the auction were bidders from the U.S., Canada, the U.K., France, Switzerland, Belgium, China, and Italy.

Gross said he began collecting the stamps in question around 2000, spending an estimated $2.5 million on them. While today's auction benefited a charitable cause, it also helped Gross gauge the market for collectible stamps. Mr. Gross is one of the largest U.S. collectors and estimates having spent between $50 million and $100 million on his collection (that's kind of a wide range, but who am I to quibble?).