Doesn't look like there is one. Look at the photo before the finish. It looks like the endgrain appears darker in some places and it's just lighting.
Only three layers - 1/2" Cocobolo top, 1 1/8" Maple, 1/4" Cocobolo back.
The top is carved so that the edge of the cocobolo only shows as 1/4", so it matches in thickness with the back plate when looking at the sides. The exception is toward the tips of the cutaways.