Presumption as to documents: documents tendered by prosecution presumed genuine and admissible unless contrary is proved. Where a document is produced, seized or received from abroad and tendered by the prosecution against a person, the court shall, unless the contrary is proved, presume the truth of its contents and that any signature or handwriting is that of the person it purports to be; if executed or attested, it shall be presumed to have been executed or attested by the purported person. Such a document is to be admitted in evidence even if not duly stamped, provided it is otherwise admissible.