The proceeds from any investments of meter deposit funds and any other earnings therefrom shall be considered to be profit derived from the investment and shall be placed in the fund from which the operation and maintenance expenses of the utility, for which the meter deposits invested were collected, are paid. The investment of such funds by the municipality shall in no manner impair its obligation to any person, firm or corporation, to refund in full any or all deposits theretofore or thereafter made.
Okla. Stat. tit. 11, § 35-102.1