I'd like to expand on my answer a bit. There are two versions of true "coreless" damascus: layered and wootz. Both of them continue to be explored, but "layered" is by far the most frequent. What KAI Shun did, was to make a production version that was both inexpensive enough to compete with mono steel knives, and provide a performance "bump." Sakai Takayuki has also recently partnered with Takefu and marketed a cost competitive product, using the same dual core steels as KAI Shun. Xinzuo/Hezhen is the first inexpensive production version of coreless with different dual core steels. However, there are limited production coreless knives with more interesting dual core steel starting at about twice the offering price of KAI Shun--with some as high as $2000 and $3000+.