Related Clues:

• Three-digit ID
• Numerical prefix, of a sort
• First three numbers, in some directories
• 1 in 1,000,000?
• One of 101 in a googol
• Prefix with triple digits
• Long-distance requirement
• Zip code component
• 407 in Orlando, e.g.
• Sudoku fill-in
• Number prefix
• Prefix for calling
• Telephone prefix assigned to a region
• Telephone prefix for a region
• Make it in spades? In short, no