This is from a video about Bizen's sword museum. At first glance I thought it was a partial samegawa wrap like on cheaper production swords but upon closer inspection, the narrow strips of wood are on the outside which seems to indicate it is indeed a full same wrap. I thought it'd be optimal to have as much of the ito to have direct contact with the same to prevent slippage due to the bumpy texture.
Since rays aren't native to Japanese waters, who did they trade with to get the skins? I wonder how they came up with the idea to use ray skins on a tsuka in the first place.