What happens next?

How to get a certificate of authenticity
Find an autograph authentication company.
Autograph authentication companies can help you verify an autograph was legitimate. They use a combination of specialized autograph authentication equipment, as well as handwriting analysis and computer technology, to ascertain if an autograph is legitimate.
If you obtained an autograph secondhand, this can be particularly helpful. If you intend to sell an autograph you obtained in person, this can also be helpful as potential buyers will know your autograph is real.