(a) As used in this Code section, the term:

(1) "Local retirement allowance" means the retirement or pension allowance payable by a local retirement system to a locally retired teacher.

(2) "Local retirement system" means a retirement or pension system of a county, municipality, or local board of education which includes teachers as members thereof or which is paying retirement or pension allowances to locally retired teachers.

(3) "Locally retired teacher" means a teacher who has retired or hereafter retires pursuant to a local retirement system.

(4) "Total retirement allowance" means the local retirement allowance plus any amounts which are payable by the board of trustees to the locally retired teacher pursuant to the provisions of this chapter other than this Code section.

(b) Any other provisions of this chapter or any other law to the contrary notwithstanding, the minimum retirement allowance provided by subsection (a) of Code Section 47-3-120 shall be applicable to locally retired teachers who, for such purposes, shall be deemed to be members of this retirement system. In determining the minimum retirement allowance payable under subsection (a) of Code Section 47-3-120 to a locally retired teacher, credit shall be given for all teaching service prior to January 1, 1945, under the local retirement system if the local retirement system did not allow its teachers to establish credit for any such service. Subject to the provisions of subsections (c), (d), and (e) of this Code section, for each locally retired teacher whose total retirement allowance is less than the minimum retirement allowance provided for by subsection (a) of Code Section 47-3-120, the board of trustees shall pay monthly directly to such locally retired teacher an amount equal to the difference between the total retirement allowance and the minimum retirement allowance.

(c) As applied to locally retired teachers who retired prior to July 1, 1986:

(1) The provisions of this Code section shall not decrease the amount payable by the board of trustees to an amount less than the amount payable pursuant to the authority of this Code section prior to July 1, 1986;

(2) Increases in the local retirement allowance granted on or after July 1, 1986, by the local retirement system shall cause the amount payable by the board of trustees pursuant to the authority of this Code section to be decreased in the same amount as the increase granted by the local retirement system; and

(3) Increases in the total retirement allowance payable to a locally retired teacher which hereafter result from new or increased allowances paid by the board of trustees to the locally retired teacher pursuant to provisions of this chapter other than this Code section and Code Section 47-3-126.2 shall not decrease the amount payable by the board of trustees pursuant to the authority of this Code section.

(d) As applied to locally retired teachers who retire on or after July 1, 1986:

(1) Increases in the local retirement allowance granted after retirement by the local retirement system shall cause the amount payable by the board of trustees pursuant to the authority of this Code section to be decreased in the same amount as the increase granted by the local retirement system; and

(2) Increases after retirement in the total retirement allowance payable to a locally retired teacher which result from new or increased allowances paid by the board of trustees to the locally retired teacher pursuant to provisions of this chapter other than this Code section shall not decrease the amount payable by the board of trustees pursuant to the authority of this Code section.

(e) Notwithstanding the provisions of subsections (c) and (d) of this Code section, if the minimum retirement allowance provided for by subsection (a) of Code Section 47-3-120 is increased on or after July 1, 1986, the amount payable by the board of trustees to a locally retired teacher pursuant to the authority of this Code section shall be the greater of either of the following amounts:

(1) The amount necessary to increase the sum of the total retirement allowance plus the amount payable pursuant to the authority of this Code section to an amount equal to the increased minimum retirement allowance; or

(2) The same amount which the board of trustees was paying pursuant to the authority of this Code section on the date the increase in the minimum retirement allowance became effective if the total retirement allowance payable on that date exceeds the increased minimum retirement allowance.