Related Clues:

• Paleontologist's estimate
• Many moons
• Secret stat, sometimes
• Paleozoic, for one
• Historical stage
• Ruth's was 2.28
• Unique stretch in time
• Paleozoic, for example
• --- of Good Feelings
• Several periods
• Twain's "The Gilded ---"
• Period piece?
• Grandma's ''secret''
• Space ___
• Important historic period