Any debentures authorized by the Land Office Building Act N.M. Stat. Ann. § 19-12-1 to 19-12-13 may be purchased by the state investment officer as an investment for the permanent funds in his hands, with the approval of the officials whose approval is required by the constitution for the investment of permanent funds. The purchase by the state investment officer may be made at private sale without the necessity of advertising and at interest rates not to exceed the per annum rate prescribed by law.