No, I wouldn't agree to hardly anything, if for no other reason, the vast array of alloys available. Only after testing it would I feel comfortable in making a commitment on value.
Years ago, a close friend, who ran a pawn shop, advanced several thousand dollars against dental alloys---and ended up taking a bath. It was badly misrepresented.
Are you familiar with test needles? They are readily available from jewelry supply houses. They can be used to judge karat fineness of gold, but the presence of the platinum group metals tends to force false readings, making you think the gold is better than it is. They work great for jewelry, however.
Harold