Widow’s annuity – All employees – Withdrawal before age 50 – Death after age 50. The widow’s annuity and widow’s prior service annuity for the wife of an employee who withdraws after service of 10 or more years before age 50, and later attains such age and dies while out of service, shall be fixed as of her age at the time the employee becomes age 50. She shall receive annuity, from the date of the employee’s death, of such amount as can be provided on a reversionary annuity basis from the following sums accumulated to his credit on the date the annuity was fixed:
     (1) If service is 20 or more years, the entire sum accumulated to his credit for widow’s annuity, and, for a present employee, widow’s prior service annuity;
     (2) If service is 10 or more but less than 20 years, the sum accumulated to his credit for widow’s annuity from salary deductions, plus 1/10 of the sum accumulated to his credit for widow’s annuity, and, for a present employee, widow’s prior service annuity, from contributions by the city, for each completed year of service after the first 10 years.