showpiece vs rariora

showpiece and rariora both are nouns.

Word	Noun	Adjective	Verb	Adverb
showpiece	Yes	No	No	No
rariora	Yes	No	No	No

As nouns, rariora is a hyponym of showpiece; that is, rariora is a word with a more specific, narrower meaning than showpiece:

showpiece: the outstanding item (the prize piece or main exhibit) in a collection
rariora: (plural) rare collector's items

showpiece (noun)	rariora (noun)
the outstanding item (the prize piece or main exhibit) in a collection	(plural) rare collector's items