I gave the shell a bit of a cleanup over the weekend, the weather wasn't ideal for full polish and wax... but it did remind me of something odd: I've tried to photograph it, but just can't get the camera to catch it - my rear screen, in certain lights or if there's a hard frost, has 300zx across the top of it - I'm assuming that it had a sticker, which has etched the glass rather than it ever being original? To be honest, I quite like it - very subtle! 

Which leads me onto the main question... I've now removed some window stickers (getgreddy for those of you with long memories!!) which appear to have also etched the glass! I've completely removed them with a blade, used isopropyl to get rid of the adhesive but you can still see where the letters were ? They will be covered up to some extent by forum stickers - but has anyone had any luck with polishing the glass - I've got a DA - but from googling, it's going to need something pretty aggressive, and I really don't want to ruin the glass! 

You could try polishing the glass with something like this which is a very mild abrasive polish:

https://www.autoglym.com/car-glass-polish