journeyman's piece
English edit
Etymology edit
Likely a calque of German Gesellenstück. Much use seems to be in reference to Germany or continental Europe.
Noun edit
journeyman's piece (plural journeyman's pieces or journeymen's pieces)
- A work that someone produces in order to prove that they have completed their apprenticeship in a craft.
- (figurative) An action or achievement by which someone proves their competency.