Mass. Gen. Laws ch. 4 § 9A
In any written instrument, a recital that such instrument is sealed by or bears the seal of the person signing the same or is given under the hand and seal of the person signing the same, or that such instrument is intended to take effect as a sealed instrument, shall be sufficient to give such instrument the legal effect of a sealed instrument without the addition of any seal of wax, paper or other substance or any semblance of a seal by scroll, impression or otherwise; but the foregoing shall not apply in any case where the seal of a court, public office or public officer is expressly required by the constitution or by statute to be affixed to a paper, nor shall it apply in the case of certificates of stock of corporations. The word "person" as used in this section shall include a corporation, association, trust or partnership.
Mass. Gen. Laws ch. 4, § 9A