Credential

a.	1.	Giving a title or claim to credit or confidence; accrediting. Their credential letters on both sides. - Camden.
n.	1.	That which gives a title to credit or confidence.
	2.	Testimonials showing that a person is entitled to credit, or has right to exercise official power, as the letters given by a government to an ambassador or envoy, or a certificate that one is a duly elected delegate. The committee of estates excepted against the credentials of the English commissioners. - Whitelocke. Had they not shown undoubted credentials from the Divine Person who sent them on such a message. - Addison.

Noun

1.

credential - a document attesting to the truth of certain stated facts Synonyms: certificate, credentials, certification

advocacy, advocating, advocation, affidavit, attestation, authority, authorization, bill of health, certificate, certificate of character, certificate of proficiency, certification, character, character reference, deposition, diploma, letter of introduction, navicert, notarized statement, note, patronage, recommend, recommendation, reference, sheepskin, sworn statement, testamur, testimonial, ticket, visa, vise, voucher, warrant, warranty, witness