纪念物 vs
纪念品:
纪念物 is the personal-keepsake side — a thing you keep because of a person or event (a deceased relative's watch, a flag from a battle).
纪念品 jìniànpǐn leans commercial — gift-shop souvenirs, mass-produced commemorative items. If a museum sells it, it's
纪念品; if your grandmother left it to you, it's
纪念物.
