3.1 Upon satisfactory results of both the audit of the
firm referred to in 2.2 and the demonstration tests referred to in 2.3, the
Administration shall issue a certificate of approval as well as a notice to the
effect that the thickness measurement operation system of the firm has been
certified.
3.2 Renewal/endorsement of the certificate shall be
carried out at intervals not exceeding three years by verification that original
conditions are maintained.