Okla. Stat. tit. 52, § 52-44: Gas to be furnished through meters at meter rates -

Exceptions.

All persons, firms, corporations or other business organizations

engaged in the business of furnishing natural gas in municipalities

in this state, to the inhabitants thereof, shall do so through

standard meters at meter rates; provided, that this act shall only

apply to towns where the population exceeds five hundred (500), and

shall not prohibit the sale of gas at a flat rate to federal, state

or municipally-owned buildings, institutions or plants; Provided

further, that this act shall not abrogate any existing contract, or

effect or change the terms or conditions of any franchise granted by

any municipal corporation prior to, and in effect April 28th, 1913.