Thank you very much for the advice that everyone submitted. I've taken it on board and therefore will wait until April or later before I consider grading it.
Even though I know its authentic, I understand there's no way to prove that since there was no witness in 1991 when it was probably signed. But if that does change, I will hopefully be able to have it graded as its 1 of 100 signed.
Lastly, @DougC thank you for the feedback, but I'm not very involved so honestly have no clue what that means. If there's a way to explain it but dumbed down, that'd be appreciated also, but if not, no worries.
Again. Thanks to everyone who gave advice on what to do. I really appreciate it.