It is one of America's treasures -- the most valuable ounce of gold in the world, the celebrated, the fabled, the infamous 1933 double eagle. It shouldn't even exist but it does, and its astonishing, true adventures read like "a composite of and (). Illegal to own and coveted all the more, it has been sought with passion by men of wealth and with steely persistence by the United States government for more than a half century.