The seams are kinda hard to see on this transparent base. Do you see where the ribbons join on the side? That's the start of the seam. And I'm not sure but it looks like there might be a line in the glass which you might be able to see or feel in hand. But I really am not sure if I'm seeing the end of the ribbons correctly. Tried to draw close to the seam with the green line.
In this view it's easier to see the ribbons coming together on the edge of the seam.
(And there will be another seam where the ribbons come together on the other end.)
If you don't see what I'm getting at, don't worry. This is a tricky one. Will be easier to pick out seams on other marbles. (: