(a) Upon completion of the installation of a pressure retaining item, or at the time of the initial permit inspection of an existing installation, each pressure retaining item shall be stamped or marked by the inspector employed by the department with a state serial number, consisting of letters and figures to be not less than 5/16 inch in height and arranged: For power boilers HAW-####-YEAR
For heating boilers HHB-####-YEAR
For pressure vessels HPV-####-YEAR
Heating boilers assigned state serial numbers prior to January 1984 had the prefix HAW NO. 0000-YEAR. In each case, the year shall be a part of the number.