Notwithstanding other provisions of this division, a sealer shall not be required to inspect, test or seal any scales or other weighing or measuring instruments to be sold for use or being used for commercial purposes and so located that the testing standards, in the amount deemed necessary for the proper testing, cannot be brought to the instrument to be tested by customary means, whenever the owner or user thereof has not rendered the instrument in question more readily available for the purpose of permitting an accurate test to be made before the end of six months after notice in writing from the sealer requiring that better means of accessibility be provided for testing

such instrument.