It shall be unlawful to use other than specifications for apparatus and chemicals and directions for testing milk and cream which conform to those adopted by AOAC International or the American Dairy Science Association with such additions as are deemed advisable to make them applicable to the provisions of this subchapter. All types of test tubes, bottles, pipettes, instruments, or specified weights used in connection with testing or determining the value of milk, cream, or other dairy products by the use of the Babcock test shall be approved by AOAC International or the American Dairy Science Association. Cream test weights shall be certified by the manufacturer as to accuracy and stamped on both top and bottom.