These machines are of The rotary, variable motion lock stitch type, with the long beak sewing hook, which draws the lock of the threads to the center of the materials, between the upper and under surfaces, thus making a firm seam of fine appearance on both sides. The specific designation of each Singer Sewing Machine consists of two numbers, separated by a hyphen or letter and stamped upon a number plate, which is attached to the machine, usually upon the arm. The number before the hyphen or letter designates the Class to which the machine belongs, and the number after, the Variety of the machine in its ("lass. When supplies for a machine are to be ordered and there is any uncertainty as to the correct numbers of needles or parts, the (-lass and Variety numbers of the machine, as shown on the number plate, should be given to ensure a correct understanding of the order.