I assume it was model magic, unless someone has specific reasons to believe othewise.
a) Model magic has some of the unusual properties mentioned by people who have received it.
b) I don't think clay means anything in particular. One might use the word clay to refer to model magic, particularly if you were choosing options from a dropdown menu. It is easily moldable, and then you let it dry and it keeps it shape.
c) The original one is model magic. That would give Chris a lot of reasons to use it. It would be the first thing he would think of. He knows it works well. It would appeal to him that he was creating a replica using the same material, we know how important he thought the original material was.
I suppose the alternative is that is a knockoff Model Magic.