Do you live near a museum with a curator or possibly a college with a professor in history?? Just guessin'.
You could post this in the "What is it?" section and include measurements and weight if possible. Someone can tell you what it is, what side used it and whether it may still be dangerous.
Not going to get a legitimate certificate of authenticity unless you take it to someone and have it authenticated in person, anything less isn't worth anything more than the cost of a piece of paper..