This isn't "really" possible. Yes it inverts slightly to your eye, and I'm not sure how that works, it's similar to how if you look down on the screen from top at a 45* angle it also appears inverted. If you max out the contrast wheel of any gameboy with backlight it will do this. whatever the screen looks like when you drag your finger down the wheel is the correct polarization. don't go all the way up because it doesn't really invert. it's not magic, but it is some sort of illusion
So are you saying that all backlight/inverted gameboys can un-invert with the contrast wheel?
My other gameboy that's modded with a LEDx3 is uninverted, but it's contrast wheel doesn't take it to inversion, it just makes the screen fully black/white at it's max setting.
The default/comfortable position on its contrast wheel is the same position that is displays a comfortable, non-inverted view on my new gameboy.
The contrast wheel does something like this:
100% up: blank
75% up: Low contrast non-inverted
50%: Crisp, non-inverted
35% down: High contrast, inverted
25% down: Inverted
100% down: blank
It's a pretty nifty illusion I suppose!
I'm going to try to replicate it on my next gameboy.