For the purpose of this subchapter, a licensed tester is any person who, having furnished satisfactory evidence of good character and having passed a satisfactory examination in milk and cream testing conducted by the Department of Agriculture or its agents, has received a certificate of proficiency from the Department. Each applicant for examination for a certificate shall pay a fee of $3.45 to the Department of Agriculture or its agents. The Department shall issue a certificate of proficiency in the name of the approved applicant and under a serial number. The Department upon receipt of this certificate of proficiency, together with the payment of a fee of $3.45, shall issue a license to the applicant good for 1 calendar year. This license shall be renewed annually without further examination at the discretion of the Department upon the payment of a fee of $3.45. Each certified tester shall post the certified tester's license in plain view in the testing room in which the certified tester is employed. The Department shall revoke the license for failure to post it as above required or for any other just cause.