Bill Gross is a billionaire fund manager for Pacific Investment Management (PIMCO) who lives in California.
He is sometimes known simply as 'The Bond King' as he is the most famous bond trader in the world, but he is at least as famous as a collector.
When doing neither he is trained in yoga by an ex-marine, and writes: he is the author of two books, including Everything You've Heard About Investing Is Wrong.
William H Gross was born in Middletown, Ohio in 1944.
He gained a BA in Psychology at Duke University, North Carolina and served in Vietnam with the US Navy before gaining an MBA from University of California at Los Angeles.
However, just as important to his career path was the developing of his gambling skills, which started with a car accident during his time in North Carolina.
Whilst recovering, Gross read a book about beating the odds in gambling.
For a while he was a professional blackjack player in Las Vegas, converting $200 into $10,000 in a mere 4 months, and has said he applies his gambling methods to financial decisions.
He is now regularly asked for his views on the financial markets.
Gross also collects rare stamps on a grand scale.
Most famously, in November 2005 he completed a collection of all the US stamps which have ever been produced.
The difficulty involved in doing this is extraordinary, as there are only a few examples of some of the kinds of stamp in existence.
The stamp required to complete the collection sums up the difficulty: a 1 cent Z grill featuring the head of Benjamin Franklin, of which only 2 copies are known to exist.
The stamp is rare for two reasons: the embossed head which was intended to make cancellation mark removal and re-use more difficult, didn't catch on, and stamps worth 1 cent were often considered disposable.
Whilst one Z grill remains in the Miller collection at the The New York Public Library, the other had been released when Zoellner dissolved his then complete US stamp collection in 1998 with the Z grill going to Donald Sundman of The Mystic Stamp Company for $935,000.
 Block of Inverted Jennies and Z-Grill |
Sundman refused to sell the stamp to Gross at any price, but agreed to swap it for the block of 4 Inverted Jenny stamps (24 cent 1918 stamps with the Curtiss JN-4 biplane in the centre printed upside-down) which Gross had bought in 2005 for $2.97m.
Gross bids anonymously at auctions (his dealer acting on behalf of 'Monte Carlo') and attempts to purchase stamps without being unnecessarily extravagant.
"Being a bond investor, I wanted it to be a hobby, but a successful one. I just didn't want to lose my shirt."
The Z grill, (arguably a bid $2m over the odds) proved the exception, as he was no longer incognito.
"I think they knew I was an eager buyer."
Now, however, Gross has decided to sell parts of his collection for charity, causing him to be dubbed the 'philanthropic philatelist' by some.
Partly this will be to fund a room in the Smithsonian museum dedicated to America's postal history - Gross is donating $8m as well as loaning three great philatelic rarities to encourage collectors of tomorrow.
Tomorrow, Gross is selling an estimated $3m of Canadian and American Civil War stamps towards this cause.
Previously, he sold a collection of Scandinavian stamps to help reduce poverty in Africa, and another collection of Great British stamps, including a very rare Tyrian Plum, with the proceeds going to Doctors Without Borders.
Gross had spent $2.5m putting the collection together, but the sales totalled a cool $10m "Four times profit, it's better than the stock market." he said at the time.
