To judge if spy sunglasses are polarized or not is the same as your judge it to common polarized sunglasses. You can try to hold the sunglasses up to a computer monitor, and let the sunglasses facing computer screen. Then look through the lenses and start to rotate the sunglasses, the sunglasses lenses will start to blur and go black.
I also bought pair of sunglasses last week. And my friend told me the way to judge whether it is polarized. The way is so easy. First of all, you should find a LED screen which should be in the open state. Then you put the sunglasses' lenses in the parallel position with the screen. You should take the advantage of the polarizing principle of polarized scope. From the working principle, you will see the color of lens change from shallow to deep and then from deep to shallow situation when you move the lenses at clockwise rotation. If not, your spy sunglasses will not have the polarized function.
Well, there are many simple ways you can use to tell if the spy sunglasses are polarized or not. First, you should look for a reflective surface, and then hold the glasses. In this way, you can watch the surface through one of the lenses. And then, you should slowly rotate the glasses to a 90-degree angle. The most important is to see if the reflective glare diminishes or increases. So if you can see a significant diminishing of the glare, the spy sunglasses are polarized. But you should remember that not all the sunglasses need to be polarized, it depends on the situation.
Well, let me give you a brief introduction to the main difference between those two. So, polarized sunglasses are specially designed for outdoor activities, especially driving. Becauseh the in course of driving, people face a lot of reflected lights which could distract them from driving. So, polarized sunglasses could help to tackle this problem, while normal sunglasses cannot. Hope you find my explanation useful.