Related Clues:

• Unidentified - not explored
• Quite obscure - like x
• Not recognised
• Nameless
• Strange — obscure
• Organisation is celebrated as not having been found out?
• Undetermined
• The ultimate in non-celebrity?
• A number to be found anon?
• Obscure; x, say, in equation
• Obscure character sought by an algebraist
• Not familiar
• Contents of trunk now no mystery
• Not recognized
• Mysterious present tied in an exotic knot