Well, if that's actually what the coins look like, then you nailed it, brother!! => they're perfect!! :high5:
When I look at a dark coin, I go to brighter light or wiggle the coin so I see a glare from the surface that shows detail. That can be done on photos also. The worst problem I'm seeing is the unsharpness. Is this a phone camera?
I'm also wondering how many lights / lamps you're using. Though my photos aren't great I find myself using three light sources for darker coins. One on both sides of the coin and one directly on the coin. I also place one of the light source near the camera lens.
Cool to see how the background changes the impact of the coin! I prefer black backgrounds too. I have developed a method of shooting my coins at a slight angle. I use the grid to correct the shape in photoshop. The dark background also makes it easier to knock out the coin to black.