To check whether a lens in polarized or not, you will need a device that has actual pixels in it like smartphone, Television, Laptop, etc. Point your polarized sunglasses towards the screen and turn them. Keep turning them until the lenses completely darken at a particular angle. If the lens darkens at a particular angle, that means its polarized. As you turn a polarized lens, you will actually see the colours changing and refracting. If you turn a non-polarised sunglass, you will see no colour change. That’s how you can tell which sunglasses are polarized and which are not.