(a) Any other provision of law to the contrary notwithstanding, any member stated in subparagraphs (b)(1)(B) through (b)(1)(E) of Code Section 47-2-110 who is subject to the involuntary separation provisions of Code Section 47-2-123 and who retires upon or after attaining the age of 55, whether or not retirement at such age is required by law, shall upon application receive a retirement allowance which shall consist of:

(1) In the case of a member with at least 20 years of service, the service retirement allowance which would have been payable upon service retirement at age 60 had the member continued in service to age 60 without further change in compensation;

(2) In the case of a member with at least 25 years of service, 75 percent of the service retirement allowance which would have been payable upon service retirement at age 65 had the member continued in service without further change in compensation; or

(3) In the case of a member with at least 30 years of service, the service retirement allowance which would have been payable upon service retirement at age 65 had the member continued in service without further change in compensation.

Any provisions of this chapter to the contrary notwithstanding, in the application of paragraphs (1) through (3) of this subsection relating to allowances other than for disability or death, projected retirement allowance computations shall be made on the basis of the member's highest total monthly earnable compensation, as reflected by monthly contributions made during the last 24 calendar months in which the member had made contributions, except that no salary increase by adjustment in compensation in any manner in excess of 10 percent during the last 12 months of membership service shall be included in the projected computation.

(b) Any other provision of this chapter to the contrary notwithstanding, any member employed by the Uniform Division of the Department of Public Safety as an officer, a noncommissioned officer, or a trooper; by the Georgia Bureau of Investigation as an officer or agent; by the Department of Natural Resources as a conservation ranger; or by the Department of Revenue as an alcohol and tobacco officer or agent or as an officer or agent of the Special Investigations Unit shall be eligible to retire at age 55 if he or she has the minimum number of years of creditable service provided in Code Section 47-2-110, and upon retirement such member shall be paid not less than the service retirement allowance which would have been payable to such member upon service retirement at age 65 without a change in compensation and with the same number of years' creditable service to which such member is entitled at the time of retirement.