This is an interesting question.
Lexan, generically known as polycarbonate, can be coated as well to improve toughness. I have seen polycarbonate scratch EXTREMELY easily - look at your CDs - and on another popular 2AA light which would get bad, deep scratches on the lens no matter how I babied it.
On the other hand my glasses, also a polycarbonate type material, have been wiped with shirts and god knows what else was handy for years and have yet to show any scratches. These are definitely multicoated - UV cut, high refraction index, hardcoat, and the works. I have confirmed through both my optician and my reading about optical glass that it's possible to hardcoat both plastic and glass with a coating that is so hard it will take silica (sand) crystals to scratch it. There are hardness ratings assigned to these and only an object of higher rating can scratch a lower one (similar to Rockwell scale used for HA and knives).
I didn't make any connection between the two until I received my Surefire SRTH, which is a really nice, exotic Turbohead - with a huge 2.5" polycarbonate bezel. I bought it with certain misgivings, thinking I would have to really, REALLY put in work to care for it.
Glad to say I was wrong. That SRTH is REALLY tough as well as functional. Interestingly, in a corner, there is a tiny little patch that looks as if the coating has come off. That's what tipped me off to the fact that these could possibly be hardcoated as well.
Surefire - it's the engineering you DON'T see, as well as the engineering that you do. Glad I bought my SRTH.
PS: I'm definitely not saying it's invulnerable and you can most certainly scratch it if you try, but at least it is treated to improve scratch resistance and I don't have to handle it with white gloves. For comparison, just try scratching one of your junk CDs or CD-R disks.. heck wipe it the wrong way and you get scratches.