Unit is a Burgess Vibrocrafter 11236 Vibro-Graver. This item untested.
According to the manufacturer:
This rugged industrial quality engraving tool makes permanent markings on the hardest steel, glass, plastic, stone, wood, or almost any hard surface. Used extensively by jewelers to make background effects on jewelry. Features a durable, tungsten carbide engraving tip, positive on-off switch, and spark-free motor that vibrate at 7200 strokes per minute. The calibrated adjustment dial changes length of stroke and depth of mark.