(a) Numbers assigned to boilers by the commissioner shall be of metal and shall be securely attached to a metal plate. Such plate shall be securely attached to the front of the boiler or front of boiler setting. Such numbers shall be not less than two inches in height for power and locomotive boilers and shall be not less than one inch in height for miniature boilers. In no case shall these numbers be removed until the boiler is permanently discontinued.

(b) No person except an inspector shall deface or remove any certificate of inspection or mark of identification number on a boiler.