United States Navy & Marine Corps Medical Shield with Caduceus Collar Device - Black / Subdued Criteria: Worn on the Navy Work Uniform and the Marines Corps Utility Uniform, the Medical Shield Collar Device is used to identify Hospital Corpsman. Hospital Corpsmen are medical professionals who provide health care to service people and their families. They serve as pharmacy technicians, medical technicians, nurse's aides, physician's or dentist's assistants, battlefield medics, and more. All work falls into several categories: first aid and minor surgery, patient transportation, patient care, prescriptions and laboratory work, food service inspections, and clerical duties.