Petty Officer First Class

Good conduct
variation,
12 consecutive years or more
of good conduct

Petty officer
first class
insignia
U.S. Navy &
U.S. Coast Guard

Petty officer, first class is the sixth enlisted rank in the United States Navy, effective September 29, 2016, however not in the United States Coast Guard, just above petty officer, second class and below that of chief petty officer. A non-commissioned officer rate, petty officer, first class is also the sixth enlisted rate in the United States Naval Sea Cadet Corps.

In the United States Navy, each rating was officially abbreviation, such as ET for electronics technician, STS for sonar technician submarines, or FT for fire control technician. The Navy now utilizes the Navy Occupational Special system and disestablished the combined rating and rank that gave the shorthand for the petty officer's rank, such as ET1 for electronics technician, first class. It is common practice to refer to the petty officer by this shorthand in all but the most formal correspondence (such as printing and inscription on awards). Often, the petty officer is just referred to by the shorthand designation, without using the surname. Thus ET1 Jones would just be called "ET1". A first-class petty officer may be generically referred to as PO1 when the sailor's rating is not known, although some prefer to be called simply "Petty Officer (last name)". To address a petty officer, one would say, "Petty Officer Smith", "Smith", or "Sailor" (the latter two forms being acceptable for use by those equal or greater in rank than the petty officer). It is uncommon to address a petty officer as simply, "Petty Officer" the way one might address an NCO in the Marine Corps as "Sergeant". Also acceptable, but archaic, would be to address a petty officer or chief petty officer of any grade as "Mister Smith" or "Ms. Smith". The use of "Ms." or "Mister" is commonly only in reference to junior commissioned officers or warrant officers.

...
Wikipedia