This Raised Some Questions
The FBI was able to possibly link the letter to Anglin's handwriting from when he was in the prison system. However, since Anglin would have been extremely old, and so they could support their original decision of declaring the men dead, they said that the letter was not authentic. But, they were thoroughly unable to prove whether the letter was real or not...
All That's Left
Although the letter had the potential to be looked into, the FBI wrote it off as an elaborate ruse that was not worth their time. That letter is likely the last piece of evidence that's connected to the Alcatraz escapees that will ever feasibly surface. Was the letter real? Well, let's look at the facts...