The puzzle involved a real-life S₂N₂-treated envelope interior. If you stare at the blurry words the right way, you can make out the following fragments: "… surfaces ie … … and also rea(ding) … … of letters we … … envelope wh(ich) … …contained th(e) … ". Our thanks to Dr. Paul Kelly for providing this real-world puzzle involving disulfur dinitride.