If you can guess what this is, you have my awe!

#RetroComputing

@gmc GameBoy-Printer paper-roll!

@wespi Wait, the gameboy printer uses this too? Also, there's a gameboy printer? Now I want one :)

It's paper for the Sinclair printer (used with the ZX81 and ZX Spectrum). It has a aluminium coating and the printer zaps a small voltage through the metal to make it turn black.

@gooseliketyping @geogoeroe