N.Y. County Law § 404
The official seals of boards of supervisors of the several counties, county seal, county treasurer's seal and the seal of the register of deeds shall continue to be the official seals, respectively, of such boards, county treasurer, surrogate and register of deeds and used as such, respectively, when authorized by law. When any such seal shall be lost, destroyed, or become unfit for use, the board of supervisors of the county interested therein or not having such seal, shall cause a new seal or seals to be made at the expense of the county. A description of each of such seals, together with the impressions therefrom, shall be filed in the office of the county clerk and in the office of the secretary of state. In counties having two county seats, a duplicate of the county seal shall be procured and kept at the county seat where the county clerk's office is not situated, at some place to be designated by the county clerk and may be used by him the same as at his office. In counties having but one court house and which is located more than five miles from the county clerk's office, a duplicate of the county seal shall be procured and kept at such court house and the county clerk may use the same at such court house. The seal kept by the county clerk in each county, as prescribed in the judiciary law, shall continue to be the seal of the county, and must be used by him where he is required to use an official seal.
N.Y. CountyLaw § 404