Historical clue formulations

• Spade, for one — 2023-10-06
• Sleuth for hire — 2021-06-07
• Philip Marlowe or Sam Spade — 2010-04-20
• ??? — 2008-09-09
• Nicholson role in "Chinatown" — 2003-03-27
• Sam Spade, e.g. — 2000-04-11