Mont. Code Ann. § 7-14-4650

All of the signatures on said bonds and on the interest coupons thereof may be printed, lithographed, or engraved facsimiles except one signature of an officer of the city or commission or a representative of the trustee, which shall be manually affixed. If any of the officers whose signatures appear upon the bonds or coupons cease to be officers before delivery of the bonds or coupons, their signatures are nevertheless valid and of the same force and effect as if the officers had remained in office until the delivery of the bonds and coupons.