Historical clue formulations

• Crude meas. — 2022-12-17
• OPEC unit: Abbr. — 2021-05-19
• OPEC units: Abbr. — 2017-09-07
• OPEC units: Abbr. — 2011-05-03
• OPEC unit: Abbr. — 2010-07-11
• Crude container?: Abbr. — 2006-07-22
• Oil shipment: Abbr. — 2004-07-25
• Tankerload: Abbr. — 1999-07-31
• Unit of oil production: Abbr. — 1998-02-24
• Crude meas. — 1998-01-17
• Oil measure: Abbr. — 1997-01-30
• Petroleum meas. — 1996-09-11