Unless the offering circular and notice of call provide otherwise, interest on coupon securities is payable in regular course of business upon presentation and surrender of the interest coupons as they mature. Such coupons are payable at participating Federal Reserve banks or by the Bureau. 8 Interest on Treasury bills, and any other bearer securities which may be sold and issued on a discount basis and which are payable at par at maturity, is represented by the difference between the purchase price and the par value, and no coupons are attached.