Collector's item in 'Twelfth Night' (5)

I believe the answer is:

curio

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'collector's item' is the definition.
(I've seen this before)

I don't understand the remainder of the clue.

(Other definitions for curio that I've seen before include "Interesting object of rarity or difference" , "Rare and unusual item" , "'Rare, unusual object (5)'" , "Object that is interesting, being rare or unusual" , "Odd, unusual object" .)

I've seen this clue in The Globe and Mail.

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