Collector's item and Nonpareil

Collector's item noun - The outstanding item (the prize piece or main exhibit) in a collection.

Nonpareil and collector's item are semantically related. In some cases you can use "Nonpareil" instead a noun phrase "Collector's item".

Nonpareil noun - Someone of such unequaled perfection as to deserve imitation.

Collector's item and nonpareil are semantically related. Sometimes you can use "Collector's item" instead a noun "Nonpareil".