But read the gadget blurb again - that's the claim, is it not? This is what we're discussing, is it not?

Contamination? Very tiny indeed - the CD itself is polycarbonate (very dimensionally stable) and the coating over the vacuum-sputtered aluminium is acrylic. All are made to very high standards of purity. There may be metallic catalyst residues in the polymers, but these would be compounds, not free metals. And having worked in the coatings industry for 20 years, I can vouch for the fact that inks also contain a very low quantity of impurities.

So, the answer to the question

Are we certain there is no ferrus content, or contamination of the material in a CD ?

is, to a very high degree, yes.