The device is called KY 717 and from what I've been able to find out, it's some sort of rectifier. The solder tab is insulated from the rest of the body.
I was unable to make a better picture. The major division on the paper is 10 mm and the device appears to be 37 mm long. The screw is from what I can see M4 type screw. The soldering hole has diameter of around 3 mm, but is deformed so my measurements could be bad.