Hvidt Chair Spline Joint  

splines
I just checked mine. I have four side chairs and two arm chairs, and I can see the splines on five of them,...but I assume the sixth chair has them also. I didn't have the best light to examine them under.

Thanks!
Thanks!

My four all have them,...
My four all have them, although they were nearly undetectable until they were refinished. A friend had six, and all of those had them as well.

Good structure,
and hard to disguise completely, as the grain directions of the two joined caps are necessarily so divergent -- the reason for the joint in the first place. I assume the rest of the back is formed veneer (plywood). At greater trouble and expense, the top caps of solid wood could have been replaced by a single piece, a curved lamination.
Flexing of the back in use would endanger the joint in the cap, unless it were reinforced as we see it. This cap stiffens the back a great deal, I would think . . .