Historical clue formulations

• Sign of availability — 2017-12-08
• Sign of availability — 2012-03-09
• Sign in a boardinghouse window — 2010-05-24
• Letter's sign — 2009-08-15
• Apartment window sign — 2007-12-18
• Sign in a house window — 2006-06-01
• Sign at a bicycle shop or boardinghouse — 2004-03-28