Longman Dictionary of Contemporary English
museum piece
noun
EXAMPLES FROM OTHER ENTRIES
▪ a museum piece encased in glass
▪ Some of the weapons used by the rebels are museum pieces.
EXAMPLES FROM CORPUS
▪ But will I been seen as a museum piece by some?
▪ Gluck was armed with an incredibly heavy musket, a single-shot museum piece with an octagonal barrel and a smooth bore.
▪ He acknowledges that liturgy is not a museum piece but needs to evolve as part of a living tradition.
▪ Now the 1986 tax-revision measure that shut down shelters and closed some loopholes might best be called a museum piece.
Wiktionary
museum piece
n. 1 (context slang English) a very old item. 2 (context informal English) an obsolete form of technology
Wikipedia
Museum Piece
Museum Piece is the second episode in the first series of the British comedy series Dad's Army, originally transmitted on Wednesday 7 August 1968.
Usage examples of "museum piece".
I can't imagine why it has trotted out a lovely old museum piece like her yonder.
I looked from the grotesque old museum piece of a gun to Ivan's face, which was no longer young and handsome.
It's a lovely six-hundred-year-old museum piece that fills up a whole room.