Manufactured in 1957 by David Mann, Incorporated, the Type 621 Mann Comparator played a key role in the crisis. A machine that enabled imagery analysts to derive very precise measurements from objects or features revealed on photographic imagery, the device enabled NPIC analysts to accurately measure the length of the tubes they discovered wile analyzing U-2 spy plane imagery and determine that they were in fact missiles. The findings were irrefutable evidence that proved for Kennedy that the Soviets were installing medium range, nuclear-capable missiles in Cuba that were aimed at the U.S. According to the University of Virginia, the comparator was capable of an accuracy of 1 micrometer while analyzing photographs of 6-10 foot resolution. This measurement was done by moving the photographic plate beneath a microscope along accurately scraped ways. By reading the dial on the X and Y direction screws, one could measure very accurately the relative positions of objects on the plates.