Credential
A credential was a qualification, often in the form of a document, that gave one standing in a field or rendered one suitable for an activity.
When Romulan Sublieutenant Setal revealed knowledge of "the incident at Galorndon Core" with the USS Enterprise-D earlier that year, Enterprise-D security chief Worf sneered, "you are aware of a great deal for a logistics clerk." Setal explained that it was common knowledge, before offering to show his rating code, a statement that reminded Worf, "forged credentials are a simple matter for a spy." (TNG: "The Defector")