Hard to tell what you see seeing. The areas you might see something on, the glare from the light maybe covering. Try rotating the coin a bit and let the light fall over that area rather than putting the spotlight on that area. The amount of light helps, but too much drowns what you want to show.
Note the light amount in this image:

I use a 14 watt bulb. Basically about as bright as a flashlight bulb. This way you can see what you want to show with out making look at your looking at the sun.

Another example of keep the light so you can see, but not drowning the image with too much light.

Another light test on this one. Although the almost proof like coins are just business strike coins, the lower left one is a proof coin. So controlling the light is a necessary factor.

Note the light direction on this coin. the light is coming from the NE to SW direction. Note how the light falls over the devices need to see. This allows the light and shadow affect needed to see what the photographer want to bee seen. But not putting a spot light on that area.
Here is another example of allowing the light to show just what you want to see.

Hope this helps.