Except as otherwise provided by law, public records shall mean all papers, correspondence, memoranda, accounts, reports, maps, plans, photographs, sound recordings, or other documents, regardless of physical form, including records produced by or for use with electronic or mechanical data processing devices, and which have been or shall be created or received by any agency or its lawful successor or official thereof in the exercise of his office or in the conduct, transaction, or performance of any business, duty, or function pursued in accordance with law, but shall not include library or museum material made or acquired and preserved solely for reference purposes, extra copies of documents preserved only for convenience or reference, and stock of publications and reproduced documents.