A magic eraser has taken dirt, splatters, and paint splatter off of it as well as most of the permanent marker, but it looks like some of the dye has soaked into fibres below the surface. I’m not sure what will remove/break down the dye that wouldn’t also harm the color of the shell or the material itself.
Funny how much dirt and dust can be on something that you don’t even notice, though, and I already went over it with a soapy cloth.
–
Found the manufacturing logo, this one has the overlapping triangles from Summit Plastics.