Historical clue formulations

• Predecessor of a copter — 2023-04-07
• Big name in bicycle helmets — 2016-10-25
• Copter's forerunner — 2012-07-22
• Not a dupe: Abbr. — 2010-09-02
• Big name in cycling helmets — 2009-05-30
• Early copter — 2007-04-28
• Early whirlybird — 2002-01-20
• Copter's forerunner — 2001-12-07
• Copter's forerunner — 1998-05-01
• Copter kin — 1994-02-06