20.(1) Where one person signs and delivers to another a paper stamped in accordance with the law relating to stamp duty chargeable on negotiable instruments, either wholly blank or having written thereon an incomplete negotiable instrument, in order that it may be made, or completed into a negotiable instrument he thereby gives prima facie authority to the person who receives that paper to make or complete it, as the case may be, into a negotiable instrument for the amount, if any, specified therein, or, where no amount is specified for any amount, not exceeding, in either case, the amount covered by the stamp. (2) The person so signing shall, subject to the provisions of sub-section (3), be liable upon such instrument, in the capacity in which he signed the same, to any holder in due course, for the amount specified in the instrument or filled up therein: Provided that no person other than a holder in due course shall receive from the person so signing the paper anything in excess of the amount intended by him to be paid thereunder. (3) In order that any such instrument may on completion be enforceable against any person who became a party thereto before such completion, it must be filled up within a reasonable time and strictly in accordance with the authority given: Provided that if any such instrument after completion is negotiated to a holder in due course, it shall be valid and effectual for all purposes in his hands, and he may enforce it as if it had been filled up within a reasonable time and strictly in accordance with the authority given.