Alright after much reflection and thought I have worked through these clues. I agree with many here that Rhodium is involved because it is mentioned, however many clues state that your answer is 79 or gold on the periodic table. As most are aware white gold is often 18K gold mixed with some other precious metals and then plated with rhodium. I am venturing to think the gentleman has sent you a piece of white gold jewelry. As jewelry can also be weighed in grams. This is my final answer.
All I have left to say is well played Mr. Bond well played!!