Historical clue formulations

• One of a kind — 2018-02-10
• Singular find — 2015-01-09
• One in a million — 2010-06-28
• Curiosity — 2002-11-13
• One in a million — 2002-01-18
• Uncommon sort — 2000-08-05
• One in a million — 1996-11-07
• Oner — 1993-11-26