Interesting observations Tallon.
Yes, when glass chips very easily on the edges, it may be a sign that it has been tempered. Tempered glass is cooled in a way that retains a lot of tension in the molecules. This causes it to be much stronger on the surface (and of course safer when it breaks) but the side effect is it doesn't like impacts on the edges. So when the smallest crack occurs on the edge, it spreads quickly. Sometimes, even striking it on a small grain of sand will cause chips but larger impacts may cause catastrophic failure (crazing into tiny round pieces - like on windows of automobiles). My guess is the factory glass is tempered but it is tough to tell. Does anyone have a picture of a broken lens? That should confirm the suspicion.
The fact that you are seeing some tiny bubbles in factory glass could be a clue about how it was manufactured. Maybe this glass was not press molded as I originally thought. Very interesting.
EDIT: I just had another thought. I was just wondering why Lamborghini, who is obsessed with saving weight on their cars, would use heavy glass headlight lenses when they could have used plastic. Perhaps one reason is they were worried about heat from the Xenon projectors warping/distorting them?
