Presumption as to documents: prosecution-tendered papers are presumed truthful and genuine unless rebutted by the accused. Where a document produced, seized, or received in proceedings under the Act is tendered by the prosecution, the court shall, unless the contrary is proved, presume the truth of its contents and that signatures or handwriting are those of the persons they purport to be, including that executed or attested documents were executed or attested by the purported persons; such documents are admissible even if not duly stamped, provided they are otherwise admissible.