With polarized sun eyes, you can see the color of the stripes, no steel should not see.
Turn an Angle, see also see whether there is wind pressure spot on glass surface actually. You will see the irregular deformation of the glass on the whole panel.
? Look at the side because when the glass is toughened, it will soften, the flatness will be worse because of the roller way, face to face, the gap in the middle is an ellipse, so it is obvious.
The flatness of toughened glass is worse than that of ordinary glass!
Simple way: two pieces of glass face each other vertically close together, look at the two long sides of the two pieces of glass together, see if there is a clear gap between the two long sides of the glass, if there is a gap is a certain arc, if so, it should be toughened. Face to face, not face to face. This is physically demanding. No, just use two X-ray films with a burst of light to see.
When you side 70 degrees look, should see the blue wind spot after toughening, the flatness of the glass also has apparent drop than the glass before toughening.