unknown hanko

Hi
I am a new member - but not new in playing shakuhachi:
http://www.komuso.com/people/people.pl?person=1547

I normaly play a Tom Deaver 1.8 and lately got 3.0 Jinashi
which plays easy and is well in tune (deep F).
It has a marking and I don't know if this could by type of an
hanko or not.

Does anyone pleas has some hints who could be the maker?



thanks.....