I think it was the great Enid Lumley, who after extensive listening tests gave pure copper the final nod. Edson Price used to make and market those in excellent quality. But then I am no expert in "metallurgy" and I would think, that the result would also depend on what material the metal in your binding posts is. I reckon gold on gold, or silver on silver, copper on copper would give the best results but have never really tested that hypothesis for myself in any serious fashion. Copper on copper works best for me, the only drag is, that it needs to be cleaned quite often. Cheers,