Try lighting the whole room and not sending any light directly at the coin. You can also try making a light tent around the whole rig and see if this works. I'm still not happy with the ringlight on curves but am trying other coins first since I have so few cups and fewer that are at all nice. This is my previous shot of this Andronicus. This is wher I am with the ring. It is closer to the coin in darkness but is not a finished product.