I think it's only on PAL gameboy pockets (but people disassemble and reassemble them to sell for money or to use themselves). Why do some of them have that sticker and which region of gameboy pocket can I use to get my gameboy cartridge to function? The cartridge is almost new and the grey gameboys are mine.
The yellow gameboy pocket is an example (you can see the EUR sticker).
People have said that they're not region locked but I don't think that's true... I had a newer cartridge than that and it wouldn't work in either of my gameboys either.
They get to the Nintendo screen and the software screen and don't proceed
One of the cartridges was French and the other is US English.
One came with a bottish customs form attached and the other came with an area for a customs form but no form attached.