Wiktionary
fourth-class
a. (context US English) A former class of mail consisting mostly of heavier printed matter
Usage examples of "fourth-class".
Magazines (already endangered by HD-video equivalents) got so full of those infuriating little fall-out ad cards that Fourth-Class postal rates ballooned, making the e-mail of their video-equivalents that much more attractive, in another vicious spiral.
He had to show his papers and was found to hold a fourth-class ration book, the kind issued to nonworkers, on which nothing could ever be bought.