The notarizing officer should prepare a caption for every deposition; should certify on the deposition that the witness was duly sworn by him and that the deposition is a true record of the testimony given by the witness; and should sign and seal the certification in the manner prescribed in §§ 92.15 and 92.16. (Rules 30 (f) (1) and 31 (b), Rules of Civil Procedures for the District Courts of the United States.)