It says the serial number is stamped in chinese on the cap? I wonder what that looks like...
There is some Kanji on the cap which makes if different from a regular black cap:

There are a few for sale on Shopping Mall Japan but for around $270...
This is more my style:
Sailor Pen Noriyoshi Nagahara award commemoration fountain pen - A Pro Gear king size with a special "2007" nib. $800 though!!!!!