Historical clue formulations

• Open, as an envelope — 2024-09-29
• Open, as a letter — 2024-06-26
• Open, as classified records — 2024-03-04
• Open, as an envelope — 2023-04-10
• Open, as a tomb — 2022-04-21
• Open — 2018-09-23
• Open, as an envelope — 2018-08-29
• Open, as a letter — 2014-09-09
• Open, as an envelope — 2012-03-20
• Open — 2012-02-05
• Open, as an envelope — 2008-04-28
• Open — 2004-05-21
• Break open — 2001-10-13
• Free, in a way — 2001-03-24
• Open — 1997-01-26