[BobC]

Got a friend who is an architect and back in the day when they actually used a pencil and paper to draw on they would have an electric eraser that they used to completely erase unwanted lines or corrections. That might be what he is referring to. You held the thing in your hand, turned it on and the eraser at the tip would rotate at a variable speed. Kind of looked like a Dremel tool if I remember correctly. Not sure if they still use them since most architects use computers and CAD programs to draw on now but, they're probably still around somewhere.