Such bonds shall be signed by the mayor and treasurer of an incorporated city, by the treasurer and selectboard or trustees, as the case may be, of a town or village, by the treasurer and trustees or prudential committee, as the case may be, of an incorporated school district, lighting or fire district, and by the treasurer and board of school directors of a town school district. The coupons to such bonds shall be signed by or bear the facsimile signature of the treasurer. When such municipal corporation has a corporate seal, such seal shall be affixed to such bonds, otherwise such bonds need not be sealed.