Identifying Luster Under Toning On MS Coins.

Every coin different. If it's not completely black for silver, or a heavy brown for copper, there certainly could be lustre showing. Think about an old tea service from the 1800's. If it's found in an attic, it will be black as can be and won't have any shine unless polished. Same for a coin; there's a point where the tarnish will eventually ruin any lustre if it goes completely black long enough, like the coin here. I don't think it would have any hidden lustre left. (not my coin)