The right to a service retirement allowance under this chapter shall vest in any member who withdraws from service with at least ten years of membership service subsequent to January 1, 1954, although he has not yet attained 60 years of age, provided that he has not withdrawn his contributions. Such member shall become entitled to a service retirement allowance (1) upon filing an application as provided in Code Section 47-2-110 and (2) upon attaining the age of 60 or, at his option, at any time subsequent thereto after filing such application. The retirement allowance in the case of any such member shall be the monthly amount he would have received had he retired on the last day he contributed to the retirement system and at that time had been the same age as when he actually retired. If a member with vested rights dies before reaching age 60, his accumulated contributions shall be paid to his named living beneficiary, otherwise to his estate.