 That this is a genuine reserve, and not the result of removal of the gesso or paint, is demonstrated by a raised edge still existing around the gesso, the result of build up from the edge of brush strokes at the edge of the gesso area.The reserve area, which was likely to have been as much as originally appears to have been trimmed at some point probably to fit a frame (we know that in the 1906 framing it was the frame itself which was trimmed, not the picture, so it must have been earlier), however at no point has any of Leonardo's actual paint been trimmed.Therefore, the columns in early copies must be inventions of those artists, or copies of another (unknown) studio version of "Mona Lisa".