Historical clue formulations

• Nautical acronym — 2007-12-27
• Guidance system at sea — 2007-03-04
• Old global positioning system — 2006-04-02
• Ship's navigation system — 2004-08-09
• Navigation acronym — 2004-03-31
• System for pilots — 2003-04-22
• Navigational aid — 2001-05-08
• Ship navigation aid — 2000-08-21
• Navigational system — 1999-09-27
• Ship's guidance system — 1996-03-04
• Navigational aid — 1995-06-04
• Navigational system — 1994-10-04