I’ve looked far and wide for data on this unit but have come up short. It seems to be a vintage model of a hardness tester. The model is an Ernst Computest. Has a date of 1998 on the back. Theres a Rockwell portable model that looks close to this so I’m guessing this may have been one of the 1st iterations. I sadly don’t have any power cords or supplies to test this unit thus so selling as is for parts or repair. If of any interest please feel free to reach out. See photos for more details. Thanks for looking!