Every public officer having in his custody any registers, books, records, papers, documents or proceedings, the inspection whereof may tend to secure any duty, or to prove or lead to the discovery of any fraud or omission in relation to any duty, shall at all reasonable times permit any person authorized in writing by the Collector to inspect for such purpose the registers, books, papers, documents and proceedings, and to take such notes and extracts as he may deem necessary, without fee or charge.