PSA/DNA or JSA.
An autograph that is not authenticated by a creditable company could sell at half the market value or less. Two of the top, and most trusted authenticators are PSA/DNA, and James...
COA.
Certificate of Authenticity - Also known as COA - A statement of the genuineness of an item (often an autograph), printed on a piece of paper, thin cardboard, that is furnished to the buyer by...
no. However you can have most (not all) items appraised by a specialist who may be able in some cases to given a new certificate, it will be dated as a second certificate but is often better than...
The Academy of Manuscript and autograph, LLC is a good place to start there website is www.autographsauthentication.com or www.autographauthenticationservices.com