Which device denotes an officer's rank insignia typically worn on both collars?

The correct answer is the gold embroidered five-pointed star. This insignia is generally associated with the rank of a rear admiral in the naval service, indicating a significant leadership position. It is typically worn on both collar points of a uniform to signify the officer's rank clearly and uniformly. The use of gold embroidery also conveys distinction and authority, consistent with the responsibilities of higher-ranking officers.

This insignia serves not only as a way to identify rank at a glance but also as a key part of the military uniform's formal appearance, adhering to regulations that govern uniformity and representation of ranks within the service.