Rating code
A rating code was the Romulan equivalent of a personal ID card or credentials.

When it was doubted that Admiral Alidar Jarok was just the low-level logistics clerk Setal, the Romulan offered to show the crew of the  his rating code to prove that he was Jetal. Worf, however, claimed that these codes could easily be forged by a spy. ()

Legal documents
Identification technology