From and after January 1, 1966, each deputy sheriff as defined in Section 9-128.1 who is a member of the County Police Department and a participant of this fund shall contribute 7% of salary for age and service annuity. At the time of retirement on annuity, a deputy sheriff who is a member of the County Police Department, who chooses to retire under provisions of this Article other than Section 9-128.1, may receive a refund of the difference between the contributions made as a deputy sheriff who is a member of the County Police Department and the contributions that would have been made for such service not as a deputy sheriff who is a member of the County Police Department, including interest earned.
Such deductions beginning on the effective date and prior to July 1, 1947 shall be made and continued for a future entrant while he is in the service until he attains age 65, and beginning on the effective date and prior to July 1, 1953 for a present employee while he is in the service until the amount so deducted from his salary or paid by him according to law to any county pension fund in force on the effective date, with interest on both such amounts at 4% per annum, equals the sum that would have been to his credit from sums deducted from his salary if deductions at the rate herein stated had been made during his entire service until he attained age 65, with interest at 4% per annum for the period subsequent to his attainment of age 65. Such deductions beginning July 1, 1947 for future entrants and beginning July 1, 1953 for present employees shall be made and continued while such future entrant or present employee is in the service.
40 ILCS 5/9-170