Pan American World Airways, Inc. $25,000. 7 1/2% Convertible Subordinated Debenture, Due January 15, 1998, Dated June 5, 1978, #RY 4684. Certificate printed by American Bank Note Company is in Very Fine Condition. Suitable for framing as a gift for collectors of U.S. Air Lines History. Convertible Subordinated Debentures are significantly less common than the Common Stock Certificates.