Japanese steel: Nakagawa, Raizin, Ocean...and a Scapin?

A bit of detective work! Comparing the details from this frame to some of the confirmed ones that he made. Such as:

• The grub screw style seat pin.
  
• Using gussets, though nothing extreme as these.
  
• Drilled holes in the lug work.
  
  

In saying that, I could still be wrong!