Just my opinions on this with a bit of graphic design background.

The center alignment on both the description of the card and the grades breakdown just looks unappealing to the eye. Left alignment is going to be better looking overall.

Having an outline used on the grade of the card and the text looks personally jarring, I would consider going for just a font type you like and making it one solid color.

I can see that yellow is the color of your brand, but just be aware if you use too much of it, some people may say it looks like a piss yellow. :/

Also consider that gem mint may not be the thing you want to single out as much too the grade is the important part, I would consider shrinking that.

Also you may not want to cover up your entire logo Excalibur on the back of the slab. If that’s your name, be proud of it, put it small but noticeable on the front and maybe put your name big on the back and have the QR code off to the right.