188. Where any document is produced by any person under this Act or has been seized under this Act from the custody or control of any person, and such document is tendered by the prosecution in evidence against him, the Magistrate shall,- (a) unless the contrary is proved by any such person, presume- (i) the truth of the contents of such document; (ii) that the signature and every other part of such document which purports to be in the handwriting of any particular person or which the Magistrate may reasonably assume to have been signed by or to be in the handwriting of, any particular person, is in that person's handwriting, and in the case of a document executed or attested that it was executed or attested by the person by whom it purports to have been so executed or attested; (b) admit the document in evidence, notwithstanding that it is not duly stamped, if such document is otherwise admissible in evidence.