Historical clue formulations

• ___ pro quo — 2021-05-17
• Pounds — 2020-03-29
• ___ pro quo — 2016-09-19
• Pounds — 2015-07-09
• British pound, informally — 2014-08-06
• Pound — 2014-05-22
• British pound, informally — 2014-03-04
• Pound sterling — 2012-04-11
• British pound, informally — 2009-05-27
• Pounds, informally — 2009-01-08
• Mouthful of tobacco — 2001-07-06
• Pound, in Piccadilly — 1999-10-03
• Pound sterling, informally — 1999-03-16
• British pound, informally — 1998-06-22
• Pounds — 1997-08-02
• Chewable wad — 1996-08-08
• Piccadilly pound — 1996-03-03