No town shall ever become indebted for any town improvements under the provisions of NRS 269.400 to 269.470, inclusive, or otherwise, by the issuance of such general obligation bonds and other general obligation securities (other than any notes or warrants maturing within 1 year from the respective dates of their issuance), but excluding any outstanding revenue bonds, special assessment bonds, or other special obligation securities, excluding any such outstanding general obligation notes and warrants, and excluding any outstanding indebtedness not evidenced by bonds or other securities, exceeding 25 percent of the total last assessed valuation of the taxable property of the town.