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This "limit snap gage" was developed by the Greenfield Tap & Die Corporation (GTD) in Greenfield, Massachusetts. It was used in World War II (WWII) for testing the size of the diameter of a round or cylindrical surface. For example, a bullet is a cylinder, and this gage can test it to determine if its diameter is too large or two small. The term "tolerance" is the permissible deviation from the correct size. If the bullet is "out of tolerance," it is either too large or too small.