Relating to the mails; pertaining to the post office. Postal currency. During a brief period following soon after the commencement of the civil war in the United States, when specie change was scarce, postage stamps were popularly used as a substitute; and the first issues of paper representatives of parts of a dollar, issued by authority of congress, were called “postal currency.” This issue was soon merged In others of a more permanent character, for which the later and more appropriate name is “fractional currency.” Abbott.