How can I verify 304 stainless steel on a commercial meat grinder?

Grade 304 cannot be confirmed by colour or a magnet. Request the mill certificate, match grade 304/06Cr19Ni10 and heat number, and list material separately for hopper, auger, barrel, knife and plate. Welds should be pickled and passivated, free of rust, with product-contact finish around Ra 0.8 µm or better. A clause merely saying "stainless steel" proves nothing; spot-check the plate or auger by oxalic-acid passivation, then reconcile nameplate, parts list and certificate before signing off.