Reasonable belief based on definite material existing at seizure...

Reasonable belief based on definite material existing at seizure is a precondition to seizing gold outside a Customs station and to shifting the statutory burden of proving its non-smuggled character. The absence of foreign markings, the gold's purity, and lack of evidence of foreign origin, illicit importation, or the manner of smuggling cannot support that belief; domestic-procurement documents must be rebutted through investigation. On these principles, confiscation was set aside and related penalties did not survive. Reliance on witness statements under Section 138B did not invalidate adjudication where no specific request for cross-examination had been made before the adjudicating authority.