Answer

An old stock or bond certificate may still be valuable even if it no longer trades under the name printed on the certificate. The Securities and Exchange Commission, SEC, provides a Fast Answers Guide to Old Stock and Bond Certificates.

On the NYU Business Library's Analyst Report page,  Mergent Events Data provides information on companies that no longer operate. Go to Corporate Actions and search by an Issuer or by a specific event such as acquisition, liquidation, etc.

The database VitalLaw provides legal information on worthless securities.

You may want to consult The Library of Congress Business Reference Service, Guide to Business History Resources, Obsolete Securities.