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If you have to put a lot of work into it so it becomes powerful, Magikarp Power.
Multiple tropes can apply to things, sure. I think in this case, the context of the example matters too. Does the item appear to be dingy/damaged? Then it leans "Excaliber". If it looks fine but just isn't recognized as being a powerful item, then it leans "Grail". It could still be both, but the context matters.

A bad/ok/useless object with its full potential not yet realised, likely as some legendary artefact, generally the wielder does not know its true power.
Edited by DestZest