Retention of seized records limited; approving authority must justify extensions and the Board can review return requests. Section 251 prescribes that where the authorised officer lacks jurisdiction, seized or requisitioned assets must be transferred to the Assessing Officer having jurisdiction within a prescribed period, who will then enable copying or extraction. The authorised officer must allow the person from whose custody material was seized to make copies or extracts in the officer's presence. Retention of seized material is limited to periods tied to assessment proceedings, may be extended only with written reasons and approval, and cannot be prolonged beyond a short period after completion of all relevant proceedings; objections to extended retention may be brought to the Board for hearing and orders.