(a) Record of Excluded Evidence. In an action tried by a jury if an objection to a question propounded to a witness is sustained by the court, the examining attorney may make a specific offer of what the attorney expects to prove by the answer of the witness. The court may require the offer to be made out of the hearing of the jury. The court may add such other or further statement as clearly shows the character of the evidence, the form in which it was offered, the objection made, and the ruling thereon. In actions tried without a jury the same procedure may be followed except that the court upon request shall take and report the evidence in full unless it clearly appears that the evidence is not admissible on any ground or that the witness is privileged.
(b) Filing. When documentary evidence is introduced in an action, the clerk or the judge shall endorse an identifying number or symbol on it and when proffered or admitted in evidence, it shall be filed by the clerk or judge and considered in the custody of the court and not withdrawn except with written leave of court.