Okla. Stat. tit. 68, § 68-2203: Tax not to exceed what ad valorem tax would have been -

Review by Oklahoma Tax Commission.

It is hereby declared to be the intention of the Legislature

that the tax herein imposed be not greater than the amount of tax

such freight line companies, equipment companies, and mercantile

companies would pay if their cars were taxed on an ad valorem basis,

including any value inuring to such cars by reason of being a part

of a going concern.

The Oklahoma Tax Commission upon the complaint of any person who

claims he is taxed too great a rate hereunder, shall take testimony

to determine whether the taxes herein imposed are greater than the

general ad valorem tax for all purposes would be on such freight

cars, if taxed on an ad valorem basis. The Commission shall have

the power and it shall be its duty to lower the rate herein imposed

to conform to the facts disclosed at said hearing.

In order to determine the amount of tax such companies would

pay, said Commission may value all cars of any company as a unit and

allocate to Oklahoma that proportion of the total value which the

Oklahoma car mileage bears to the total car mileage of the cars of

any such company during the twelve-month period ending on December

31 of any year, and may then apply to such value so ascertained the

average ad valorem tax rate applied to property throughout the state

for that calendar year.