rank insignia; badge of rank
Refers to the physical emblem or patch worn on a uniform to indicate rank, especially in military, police, or other hierarchical organizations.
He had a colonel's rank insignia on his shoulder.
Police officers' rank insignia are attached to the chest or collar of the uniform.
記章 is a general term for a badge or medal, often commemorative, whereas 階級章 is specifically for indicating rank.
Compound of 階級 (rank) + 章 (badge, emblem).