"Based on its apparent brightness, dynamicist Bill Gray calculates that it would have a diameter of about 160 meters (525 feet) if it were a rock with a surface

"Based on its apparent brightness, dynamicist Bill Gray calculates that it would have a diameter of about 160 meters (525 feet) if it were a rock with a surface reflectivity of 10%." It is, of course, almost certainly a rock. But as a pointless mental exercise, how large would it be if it were a shiny metal probe?