Historical clue formulations

• Gold leaf, e.g. — 2015-12-05
• Tracing paper, e.g. — 2011-11-13
• Superimpose — 2000-05-28
• Cover — 2000-03-11
• Transparent sheet — 1996-09-20
• Superimpose — 1995-04-22
• "Gray's Anatomy" feature — 1994-11-20
• Make too many eggs? — 1994-06-02