5 francs Hercule de Dupré Epreuve de contrôle

The "épreuve de contrôle" is a specific category of French mint artifact — a lead striking used internally by the Monnaie de Paris to verify die alignment, depth, and relief before committing to production runs in silver or other final metals. These are not trial pieces in the commemorative sense; they are working documents, produced in lead precisely because its softness captures die detail under lower pressure and reveals flaws that harder alloys might mask.

The GEM references 159.1 and 159.2 suggest two die states or striking variants were formally catalogued, which is unusual and implies documented die progression at the control stage.