Petty officer

A petty officer is a non-commissioned officer in the navies of many countries. In the United States Navy, it is a pay grade of E-4 to E-9. Petty officers who are E-7 to E-9 are called "Chief", "Senior Chief", or "Master Chief" Petty Officers. Petty officers are managers for sailors that work for them. They are managed by officers and do work that they are told to do. Petty officers are often told to manage seamen and lower ranked petty officers.
In the United States Navy, petty officers are promoted by taking a test and being evaluated every year. If they do good enough, they are promoted to the next rank.
Badge.
The badge that a petty officer wears is used to show the rank of the person wearing it. In the United States, petty officers have been wearing a badge since 1841.