So, it's a pretty simple question. When, and how many times has the nuclear brief-case or it's Russian counterpart ever been opened with the intent of use for a nuclear launch? Are there records of such things? Obviously, they've never been used to completion, but I'd be interested to know if any sitting president or premier has felt it was necessary to do so.
The Norwegian Rocket Incident appears to have prompted the opening of the Russian Federation's briefcase. That Wikipedia article says that was the only such incident, but that seems unlikely to me.