It's a replacement battery cover for the TI-84 Plus CE PYTHON; I found there are models for the TI-84 Plus but not the CE PYTHON series.

I imagine you could add your own printed in designs, like patterns, textures or colors especially if you have a filament switching printer. Might also be a good idea to add a few sticky rubber dots on the back to keep the calculator from sliding around on the table.

Feel free to message me about this project.