When in any fiscal year ending after June 30, 2006, the state collects net severance tax on the privilege of severing, extracting, reducing to possession or producing coal for sale profit or commercial use imposed by section three, article thirteen-a, chapter eleven of the code, that is in excess of the net amount of the tax collected in fiscal year 2006, fifty percent of the difference shall be deposited in the old fund created in article two-c of this chapter. For purposes of this section, the amount of the additional severance tax on coal imposed pursuant to section six, article thirteen-a, chapter eleven of the code, collected each fiscal year for the benefit of counties and municipalities as provided in said section six, shall be excluded when determining the amount of the tax imposed by section three, article thirteen-a, chapter eleven of the code, that is collected each fiscal year from the privilege of severing, extracting, reducing to possession or producing coal for sale, profit or commercial use. The provisions of this section shall not be effective after June 30, 2009.