This is a vintage Starrett No. 230 micrometer, made in the United States, with a maximum measurement of 1 inch and a minimum measurement of 0 inches. The micrometer type is an outside micrometer with a mechanical reading, and it has a resolution of 0.00100 inches. The micrometer comes with a locking nut and ratchet top, but it does not come with a case. This micrometer is perfect for use in metalworking inspection and measurement, as well as in CNC, metalworking, and manufacturing. It is a reliable and durable tool that is sure to meet your measuring needs. Whether you are a professional or a hobbyist, this vintage Starrett micrometer is a great addition to your collection.