The CPI takes a constant basket of goods and sees how the price changes from year to year. If the price of the basket of goods increases, then there is price inflation. If the price of the basket of goods decreases, then there is deflation.
Copper and tin mainly make up bronze but other elements include phosphorus, manganese, silicon and aluminium.
Bronze is an alloy of tin, copper and other metals. Gold is mixed with other metals to create jewelry - 24 carat is all gold, 12 carat is 50% gold and 50% other metals. I would recommend gold over bronze, but in this case, I would investigate a little more to be sure what the piece is made of.