All records required to be kept under this part, including copies of authorizations, claims, inventories, notices, reports, returns and schedules, shall be retained by the manufacturer for three years following the close of the calendar year in which filed or made, or in the case of an authorization, for three years following the close of the calendar year in which the operation under such authorization is concluded. Such records shall be kept in the factory or a place convenient thereto, and shall be made available for inspection by any appropriate TTB officer upon his request.