Every official and the head of every department, board or commission of the county shall, during the month of July of each year, furnish the director of finance a detailed list of all property under his custody or control or used by him or his subordinates, owned by the county or any agency thereof, which list shall be in such form as the director of finance shall prescribe and shall be certified as true and correct by the head of each department or official furnishing same. (Mont. Co. Code 1965, § 6-1; 1941, ch. 740.)