Possible Clues:

• Rare and unusual item
• Get wretch to switch positions, a rare thing
• Object interesting because rare or unusual
• Collector's item for the duke of Illyria
• Unusual article
• Item of bric-a-brac
• It's not everyday a physicist gets round to substitute experiment's launch
• Primarily collectible, usually rare, intriguing object
• Interesting object of rarity or difference
• Object that is interesting, being rare or unusual