bond certificate,
bond United States civil rights leader who was elected to the legislature in Georgia but was barred from taking his seat because he opposed the Vietnam War (born 1940)
debenture -
A type of bond secured only by the general credit or promise to pay of the issuer, now commonly issued by large, well established corporations with adequate credit ratings.
Wikipedia
A debenture is a document that either creates a debt or acknowledges it. In corporate finance, the term is used for a medium- to long-term debt instrument used by large companies to borrow money. In some countries the term is used interchangeably with bond, loan stock or note.