I found my way over to Raukuten International about a week ago to browse their Spydercos. It is a little like a Japanese version of Ebay.
I instantly found one seller (Asagaya Shinkai) that had a bunch of weird Spydercos that I had never heard of. Among them were some very odd looking workers. A quick Google search revealed that these were rare, Japan-exclusive Workers made by G. Sakai.
I ordered three of them, and a few days later, they arrived!
The only info that I could find is:
1. The Spyderco "Everest" is a C01 Worker blade in a C13 Pro-Venator handle. It has a blue mountain symbol with the words EVEREST 1991. It was apparently made to commemorate the Swedish Everest expedition, as that expedition carried blue Spyderco Delicas.
2. The Cocobolo inlaid knife is also a C01/C13 hybrid, but with the Kraton replaced with wood. The mother-of-pearl (MOP) version has the entire scale covered by the embellishment, so I don't know if it, too, is a C13 hybrid or a straight Worker.
3. Rycen posted a thread a long time ago with pictures of the Cocobolo and MOP Workers, claiming that they are Moki factory customs. So at least one other person has a set.
Any info that anyone has is greatly appreciated. Oh, and BTW, these models need to make their way into Spydiewiki.
Pictures! In the first pic, the top knife is a regular (full-production albeit discontinued) C13 Pro-Venator.