Duty-free import of prototype machinery permitted subject to re-export undertaking, security by bank guarantee or duty deposit and sealing. Prototype or sample machinery imported for further manufacture or for use in export production can be admitted duty free up to a low-value threshold when defaced or made unsaleable; clearance may be on the basis of a bank guarantee or duty deposit and an undertaking to re-export within the temporary import period. High-value demonstrative machinery requires an undertaking limiting use to declared demonstration locations, and Customs may seal the machinery during transit, unsealing only at the place of operation.