Civilians assigned to the duties formerly assigned to local inspectors and their assistants, prior to Reorganization Plan No. 3 of 1946 (3 CFR, 1946 Supp.), and customs officers and employees, while performing duties in connection with the inspection of vessels or their equipment, supplying or signing on or discharging crews of vessels, at night or on Sundays and holidays, shall receive extra compensation to be paid by the master, owner, or agent of the vessel to the local United States collector of customs or his representative. (See § 9.16.)