The right and left images compare two cartridge cases fired from pistols manufactured consecutively at the same factory. Forensic examiners compare images such as these in order to determine whether a specific weapon can be matched to a bullet or casing found at a crime scene. Consecutively manufactured weapons create similar patterns on a cartridge case. Researchers use them to develop measurement standards that help forensic examiners identify matching cartridge cases with certainty. NIST standard cartridge cases allow examiners to rule out the possibility that an apparent match was fired by a weapon made on the same assembly line.