Section 20. Copies of hospital records kept in accordance with section seventy of chapter one hundred and eleven, certified by the persons in custody thereof to be true and complete, shall be admissible in evidence in proceedings before the division or any member thereof. The division or any member, before admitting any such copy in evidence, may require the party offering the same to produce the original record. All medical records and reports of hospitals, clinics and physicians of the insurer, employer, or of the employee shall be filed with and open to the inspection of the division so far as relevant to any matter before it. Such reports shall be open to the inspection of any party.