Historical clue formulations

• One doing carbon 14 testing — 2016-08-01
• Antique dealer, at times — 2010-03-25
• One going out — 2005-02-26
• Office stamp — 2004-08-17
• Library device — 2002-07-10
• Library device — 2002-04-17
• Post office gizmo — 2001-02-23
• Librarian's gadget — 2000-10-19
• Post office gizmo — 1999-12-21
• One playing the field — 1998-03-15
• Library gizmo — 1997-12-01
• Library gadget — 1994-09-05
• Mailroom gizmo — 1994-03-18