52 Pa. Code § 31.43
Identification of equipment regulations applicable to common carriers, the provisions of which are set forth in § 31.33 (relating to identification of equipment), except that markings shall specify the classification of contract carriers as follows:
‘‘Pa. P.U.C. No. P.’’
The provisions of this § 31.43 adopted April 11, 1939; amended through April 1, 1967.