This is called the "Gold Line" mug & it is only available at the Sega Shop online. It's a standard black ceramic mug (same as the one above) but this has a yellow/gold line art theme. It has a sketchy line-art thumbs-up Sonic overlapping a large circle design.

The circle is full of thin rays originating from a sparkling ring. There's Japanese text curved along the other edge of the circle, but the Sega Shop doesn't tell you what this says. (Does anybody know? Write in if you can translate this text for credit) The other side of the mug is blank. The line art in bright yellow on the black, plus the detailed design make this a classy mug with a pretty different look from the rest. *It doesn't seem like a good move to not tell people what the mug says, even if it is something mundane.