At first, I thought that the bonds were real, on the grounds that a fake $500 million bearer bond would be (I thought) impossible to unload. But I was corrected with a 2002 story (http://www.bizjournals.com/denver/stories/2002/10/07/daily40.html) showing that bonds in this denomination are forged.
So I now believe that they are fake. Which makes the release of the two men very mysterious, and causes me to think it was a Mafia operation.
I’ll point out that if this is a government operation, it is NOT an operation to quietly unload T-bills. Completely bypassing the issue that bearer bonds are not needed to quietly unload something, a government could have stuck them in a diplomatic “black bag”. If this is a government operation, the intent was for the men to get caught, possibly to make an anonmyous gift of several billion to the cash-strapped Italians.
Thank you Professor now I can stop wondering.