(a) All persons receiving benefits from the system on June 30, 1978, and all persons who subsequently become entitled to receive benefits as beneficiaries of persons receiving such benefits on said date shall receive those benefits to which they are entitled under the provisions of chapter 167, in effect on June 30, 1978.

(b) Notwithstanding the provisions of subsection (a) of this section, all persons receiving retirement benefits from said system on June 30, 1978, shall be eligible for an annual cost-of-living allowance in accordance with the provisions of subsection (j) of § 10-183g.

(c) Any additional credited service purchased by June 30, 1978 or being purchased on that date, provided the purchase is completed in accordance with the terms of the purchase, shall be deemed to be additional credited service purchased in accordance with the provisions of this chapter.