I've sent multiple marbles vacuum-packed in tubes made from seal-a-meal bags.
I have also rolled them up in thin packing foam with a disc of the same material separating the mibs - sort of like packing pennies in a paper tube.
The second option is the easiest, and the easiest to unpack too.
I agree, it looks like a patchy cork or a corky patch, and the colors do look Akro to me. I just don't think I've seen them all on the same marble before. But something seems a little off too so I'm having a hard time committing.