Any of the officers, after filing with the secretary of state his manual signature certified by him under oath, may execute or cause to be executed with a facsimile signature in lieu of his manual signature any security authorized in the Southern Sandoval County Arroyo Flood Control Act; provided that such a filing is not a condition of execution with a facsimile signature of any interest coupon, and provided that at least one signature required or permitted to be placed on each such security, excluding any interest coupon, shall be manually subscribed. An officer’s facsimile signature has the same legal effect as his manual signature.