Onus of disproof of signature, admissible in evidence

If any person whose duty or interest it is to deny or disprove the validity of any signature or seal, or other matter or thing, declared in section to be receivable in evidence without any proof, denies and takes upon himself to disprove the validity of that signature or seal, or matter or thing, he shall be permitted to do so, but the proof of the invalidity shall rest entirely upon that person.