This standard describes the various types and classes of cold-water displacement meters with bronze main cases, in sizes 1/2 in. (13 mm) through 2 in. (50 mm), and the materials and workmanship employed in their fabrication. The displacement meters described, known as nutating-disc or oscillating-piston meters, are positive in action because the pistons and discs displace or carry over a fixed quantity of water for each nutation or oscillation when operated under positive pressure. Major revisions made to the standard in this edition include the following: fire-flow meter use has been clarified (Sec. II.A); new text has been added to number-wheel numerals (Sec. 4.3.3.2); mechanism details section has been removed (Sec. 4.3.3.3); a footnote to safe maximum operating capacity has been added (Table 1, p. 9); text has been added to register dial type (Sec. B.2); and, the time that the test pressure is to be applied has been added to pressure tests (Sec. B.3.2).