(a) Unless for good and sufficient cause he shall make an order to the contrary, the commissioner shall issue a certificate of competence to each applicant whose application has been accepted and who has:

1. (1) taken such examination with a result finally certified as satisfactory; or
2. (2) not taken such examination but has filed with the commissioner such evidence of competence as the commissioner in his discretion may deem proof of the applicant's sufficient knowledge of the construction, installation, operation, maintenance and inspection of boilers. For illustration and not by way of limitation, such evidence may consist of relevant experience or achievement in the Civil Service of this or any other state, the United States, a qualified city, or in industry.