No person holding office under the United States shall be eligible to the office of county controller during his continuance in office as aforesaid, nor until one year thereafter; and the county commissioner, county treasurer, prothonotary, register of wills, clerk of the courts, recorder of deeds, sheriff and district attorney and their chief clerks or deputies shall be ineligible, for two years, to the office of county controller, provided the said controller shall always be eligible to re-election or appointment.
16 P.S. § 7352