Quoted from Chitownpinball:

My understanding is that they wont scratch unless you like, put a screw driver over them or something...

Quoted from Joydivision:

I pulled my Firepower protector off, the suspect white spots were not mould, they were a few very small debris particles stuck to the back - probably there from new as I didn't wipe the back down before installing or the particles made their way underneath over time. Smaller particles had accumulated around giving the effect of mould spores. Wiped it all off & reinstalled - all good. Next time I will give the back a light wipe & check before installing.
I also noticed that not much dust had collected underneath the protector after more than a year - so that's good. Wiping my finger accross the playfeld I couldn't even see dust on my finger. I don't expect the spots to reappear now, if they do, I won't be worried about it as it's not mould - I didn't actually even notice there spots until I was made aware & looked up close.
The white partcles may be from post rubber that has rubbed off & has collected in spots, which is why it appears white & seems to stick a little as well.

Quoted from Hdmike444:

So I just got home to find my playfield protector have been delivered unfortunately it was sticking out of the box and broken [quoted image][quoted image]