N.Y.C. Admin. Code § 7-620: § 7-620 Preserving and copying records.

Whenever by reason of age, exposure or any casualty, any public records, maps or papers in the custody of the register shall become mutilated, obliterated or rendered unfit for public service, it shall be the duty of the register to cause copies thereof to be made and certified for public use, and such copies when so made shall for all purposes take the place of the original records.