I took the liberty to throw the Verviers on both varieties in the 11/0 size. Measuring at various point and across several axes, the differences are negligible so the TN is either made of a different material, or deliberately debated for some other reason.
I do note that they seem to be fabricated by different processes as the TN has notch marks near the bends due to whatever holding/bending tool they use, where the TG does not. This would make it slightly weaker.