The recorder shall have custody of, and preserve in the recorder's office, the city seal, the public records, original rolls of ordinance, ordinance books, minutes of the board of commissioners, contracts, bonds, title deeds, certificates, and papers, all official indemnity or security bonds, except the recorder's bond, which shall be in the custody of the mayor, and all other bonds, oaths and affirmations, and all other records, papers, and documents not required by this charter or by ordinance to be deposited elsewhere, and register them by numbers, dates, and contents, and keep an accurate and modern index thereof.