Historical clue formulations

• Imperial title — 2021-09-25
• Kind of roll — 2020-09-26
• Frederick III, for one — 2018-08-19
• Old German ruler — 2016-08-09
• Kind of roll — 2008-10-11
• Onetime German leader — 2007-10-02
• Old German ruler — 2000-04-24
• Royal German — 1999-08-04
• Popular roll — 1995-11-09