Related Clues:

• Closer to extinction, perhaps
• Not to be had
• Bibliophile's label
• Not as common
• One-in-a-million
• Far from frequent
• Of interest to collectors, say
• Chophouse request
• Atypical
• Quite unusual
• Like a 1943 copper penny
• Harder to come by
• Out of the ordinary
• Facing extinction
• Answer to a waiter, sometimes