Possible Clues:

• 100 yrs
• 100 yrs.
• 100-yr. period
• Long time: Abbr.
• Historic span: Abbr
• Fivescore yrs.
• Mid.
• 1900s, e.g.: Abbr
• 2000s, e.g.: Abbr
• Noted arcade classic, and this puzzle's theme