Sec. 4.

The tax shall be at the rate of 55 cents in a county with a population of less than 2,000,000 and not more than 75 cents as authorized by the county board of commissioners in a county with a population of 2,000,000 or more for each $500.00 or fraction thereof of the total value. A written instrument subject to the tax imposed by this act shall state on its face the total value of the real property or there shall be attached to the instrument an affidavit declaring the total value of the real property. The form of the affidavit shall be prescribed by the state tax commission. In the case of the sale or transfer of a combination of real and personal property the tax shall be imposed only upon the transfer of the real property, if the values of the real and personal property are stated separately on the face of the instrument or if an affidavit is attached to the instrument setting forth the respective values of the real and personal property.