Keep variants identifiable
Label containers so the supplier can match their contents to the purchase order and drawing revision. Separate similar-looking part numbers and lots. If each part already has a temporary identifier that links it to a required serial number, explain that relationship and how it must be preserved. Avoid mixing loose components whose identities cannot be reconstructed reliably.
State handling restrictions
Identify cosmetic surfaces, fragile features and any cleanliness requirements. Agree on whether existing packaging can be reused for return shipment. Include the required orientation or protective separation where it matters. Packaging instructions should protect the completed mark as well as the original component finish.
Reconcile before and after shipment
Record quantities and any relevant identifiers when parts are sent. Agree on how shortages, damaged incoming parts or rejected items will be reported. At return, compare the accepted quantity and records with the release. Keep rejected or unprocessed parts clearly separated and identified. This avoids treating every returned item as accepted production simply because it came back in the same box.