The original typescript of the deciphered Zimmerman Note (or Telegram) has been found.
When I was in High School and first heard about the Zimmerman Note I was pretty skeptical. I remember asking the teacher if it was a forgery and he said he didn't think so, but he wasn't sure. So, I was assigned the task of finding out if anyone had settled that question. And, someone had - Zimmerman himself. He stupidly owned up to it a few days after it became public. It was stupid because there were a lot of people in the US at the time who assumed it was a British forgery (today's phrase would be dirty trick, I assume).