Historical clue formulations

• Mine entrance — 2019-06-16
• Mine entrance — 2016-06-04
• Mine entrance — 2012-01-14
• Shaft entrance — 2010-10-02
• Mine entrance — 2010-09-19
• Colliery access — 2010-06-26
• Mine opening — 2009-07-08
• Passage to get 8-Down — 2008-05-31
• Miner's entry — 2008-02-20
• Access for a collier — 2007-12-20
• Mine passage — 2006-07-01
• Mine access — 2005-03-04
• Mine opening — 2004-11-09
• Miner's entry — 2003-09-11
• Mine entrance — 2002-11-30
• Mine entrance — 2002-10-20
• Shaft's end — 2001-08-08
• Collier's entrance — 1998-10-31
• Pit passage — 1998-06-13
• Mine entrance — 1994-05-15