Mo. Rev. Stat. § 169.580
Any person who served as a teacher in the public schools of this state and who retired prior to July 1, 1957, under the provisions of chapter 169, shall upon application to the state department of elementary and secondary education be employed by the department as a special advisor and supervisor in connection with state educational problems. Any person so employed shall perform such duties as the commissioner of education directs and shall receive a salary of seventy-five dollars per month, payable in semimonthly or monthly installments, as designated by the commissioner of administration, out of the general revenue of the state pursuant to appropriations for the purpose, except that the payment to the retired person for such services, together with the retirement benefits he receives under chapter 169, shall not exceed one hundred fifty dollars per month. The employment provided for by this section shall in no way affect any person's eligibility for retirement benefits under chapter 169.
(L. 1965 p. 298 § 1, A.L. 1980 H.B. 1266)