The invention in question may be exhibited or demonstrated during the interview by a model or exhibit thereof. A model or exhibit will not generally be admitted as part of the record of an application. See 37 CFR 1.91. However, a model or exhibit submitted by the applicant which complies with 37 CFR 1.91 would be made part of the application record. See MPEP §§ 608.03 and 608.03(a).
If the model or exhibit is merely used for demonstration purpose during the course of the interview, it will not be made part of the record (does not comply with 37 CFR 1.91). A full description as to what was demonstrated/exhibited must be made of record in the application. See 37 CFR 1.133(b). Demonstrations of apparatus or exhibits too large to be brought into the Office may be viewed by the examiner outside of the Office (in the Washington, D.C. area) with the approval of the supervisory patent examiner. It is presumed that the witnessing of the demonstration or the reviewing of the exhibit is actually essential in the developing and clarifying of the issues involved in the application.