The several subtreasuries.
The engineer department at large.
(b) All executive officers and employees outside of the District of Columbia not covered in (a), of whatever designation, whether compensated by a fixed salary or otherwise—
Who are serving in a clerical capacity or whose duties are in whole or in part of a clerical nature.
Who are serving in the capacity of watchman or messenger.
Who are serving in the capacity of physician, hospital steward, nurse, or whose duties are of a medical nature.
Who are serving in the capacity of draftsman, civil engineer, steam engineer, electrical engineer, computer, or fireman.
Who are in the service of the Supervising Architect's Office in the capacity of superintendent of construction, superintendent of repair, or foreman.
Who are in the service of the Treasury Department in any capacity except those in the life-saving service.
3. The custom-house service shall include the officers and employees serving in any customs district whose employees number as many as five who have been or may hereafter be classified under the civil-service act; and whenever in any customs district whose officers and employees number less than five the number of officers and employees shall be increased to as many as five the Secretary of the Treasury shall at once notify the Commission of such increase and the officers and employees in said district shall be included within the classified service from the date of said increase.