Okla. Stat. tit. 68 § 2855
Every sleeping-car company and parlor-car company engaged in business in this state shall file with the Oklahoma Tax Commission a statement under oath, showing the aggregate number of miles made by cars operated by such company over the several lines of railroad in this state during the fiscal year next preceding the date of such statement; the total number of cars owned by such company and the total value thereof and the average number of miles traveled by cars of the particular class covered by the statement in the ordinary course of business during the fiscal year, and it shall be the duty of the State Board of Equalization to ascertain the number of cars required to make the total mileage of cars of such corporation within the period of one (1) year. Said Board shall ascertain and fix a valuation upon each particular class of said cars, and the number so ascertained to be required to make the total mileage of the cars of each such corporation, within the period of one (1) year, shall be assessed to the respective corporations, and such assessment shall be included in the record of the proceedings of the Board and shall be certified by the State Auditor and Inspector to the county clerks of the several counties of the state wherein such cars are operated in the same manner as property of the other railroads, air carriers and public service corporations is certified and returned.
Okla. Stat. tit. 68, § 2855