Osama Bin-liner writes George Bush a personal handwritten letter - thus proving he is still alive

After numerous rounds of "We don't even know if Osama is still alive," Osama himself decided to send George W. Bush a letter in his own handwriting to let the President know he was still in the game.
Bush opened the letter and it appeared to contain a single line of coded message:

370HSSV-0773H

Bush was baffled, so he e-mailed it to Condi Rice. Condi and her aides had no clue either, so they sent it to the FBI.
No one could solve it at the FBI so it went to the CIA, then to the NSA.
With no clue as to its meaning they eventually asked Britain's MI-6 for help. Within a minute MI-6 called the White House with this reply, "Tell the President he's holding the message upside down."