The order of adoption by which each rule is adopted by an agency shall contain all of the following:

(1) The date the agency adopted the rule;

(2) A concise statement of the purpose of the rule;

(3) A reference to all rules repealed, amended, or suspended by the rule;

(4) A reference to the specific statutory or other authority authorizing adoption of the rule;

(5) Any findings required by any provision of law as a precondition to adoption or effectiveness of the rule; and

(6) The effective date of the rule if other than that specified in RCW 34.05.380(2).