Specify the layer that carries the mark
A finished part may have paint, anodizing, plating or another treatment over its base material. The desired visual result does not tell a supplier which layers may be disturbed. Include the complete finish callout and identify protected areas. If exposing the base material is unacceptable, make that explicit before a sample is processed.
Evaluate the finished component
A useful sample includes the actual coating system, thickness range and surface preparation used in production. A spare piece of bare metal is not an equivalent trial. Examine edges of the marked area as well as the center. Ask how the component will be cleaned and handled afterward, and define whether touch-up is permitted.
Control changes between orders
A coating supplier change can matter even when the drawing number stays the same. Color, preparation and treatment changes should be communicated to the marking supplier. Store an accepted sample or clear reference with the order record. When a revised finish is introduced, plan a new first-piece review instead of assuming that the old setup will produce the same appearance.