What are the spots on my rear window?

I can see spots appearing in the rear window of the new Falcon I am driving. I have been involved in the automotive industry for approximately 25 years in dealerships with a variety of makes and I do not recall ever seeing this before. These spots range from a 5 to a 10 cent in size and cover the whole rear window nearly in symmetrical lines. I can only see them when I am wearing my polarised sunglasses. They are a greyish white and become distracting when the sun hits the rear window at the right angle. They are visible from both inside and outside the vehicle but only when wearing sunglasses. As I am on the road all the time I need to wear sunglasses for my eye protection. I started looking at all the cars on the road and found most didn't have spots visible but the ones that did were either Ford Falcons or Toyotas Corollas and Camrys, so it appears only some cars manufactured in Australia seem to have it.