Section 90C1/2. A state employee or member of the state teachers' retirement system who has been retired under the provisions of this chapter or similar provision of earlier law on a superannuation, accidental disability or ordinary disability retirement allowance and who has completed at least 25 years of creditable service shall have his retirement allowance increased to an amount not to exceed $15,000; provided, however, that such allowance shall be subject to the provisions of paragraph (e) of section 102.