Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 35, § 39H

In any county a majority of the commissioners by a writing bearing their written signatures and filed in the office of the treasurer of the county, which writing shall be open to public inspection, may authorize said treasurer to cause to be engraved or printed on any bond which said county is authorized to issue, facsimiles of their signatures, and such facsimiles so engraved or printed shall have the same validity and effect as their written signatures.