Historical clue formulations

• Naval petty officer: Abbr. — 2019-09-24
• Navy petty officer: Abbr. — 2018-03-18
• Naval petty off. — 2014-09-27
• Certain petty officer: Abbr. — 2014-06-15
• Naval petty officer: Abbr. — 2014-04-20
• Naval petty officer, briefly — 2012-09-22
• U.S.N. clerk: Abbr. — 2009-01-15
• U.S.N. clerk: Abbr. — 2004-07-11
• U.S.N. petty officer — 1996-08-01