A dropping allowance may be established by the Adjutant General as an item of the budget of the State Military Department and included in the regular appropriations made by the Legislature from time to time for the organization and maintenance of the National Guard of Alabama, based on not more than $4 per enlisted man per year. Expenditures therefrom will be for federal property shortages of National Guard organizations that cannot be covered by reports of survey, due to certain technical requirements, of the federal government. The annual estimate of this allowance shall be based on the actual enlisted strength of the National Guard and Naval Militia on the last day of September of each year. The funds expended as a dropping allowance shall be audited and accounted for in the same manner as other state funds which have been appropriated for military purposes; provided, that the dropping allowance shall not exceed $10,000 per annum; and provided further, that the provisions of this section shall be retroactive so that all property shortages existing on September 10, 1973, in addition to those that may occur thereafter, may be satisfied by the use of appropriations made in the future for the purpose of carrying out the intent of this section.