i dont believe in BU either, i have no issues with toning, its a natuaral proccess, a coin can still tone but be UNC, it should be based on the wear in my view, i have a couple of coins that to the eye look like unlustred coins, BUT you shine it in the light it has that reflective effect from the lustre, and the key is, little wear, it doesnt detract from the grade in my oppinion