Section 17. Every officer of a city who makes or executes a contract on behalf of the city shall furnish said contract or a copy thereof to the city clerk and the city auditor within one week after its execution; and the city clerk shall keep such contract or copy on file, open to public inspection during business hours. Such contracts or copies shall be kept in a book by themselves or in several books, arranged according to the subject of the contract, or in other convenient form, and an index to the subject matter of the contracts and to the names of the contractors shall be made semi-annually, and shall also be open to public inspection in some convenient form. All allowances under and additions to such contracts, or copies thereof, shall be filed with the city clerk and the city auditor, together with a sworn statement of the officer making such allowances or additions that the same are correct and in accordance with the contract. A city clerk or other city officer failing to comply with this section shall be punished by a fine of not less than ten nor more than one hundred dollars.