I believe the cels Studio Pierrot had were 
repros. ISL has the same cel as you at her 
gallery: http://earth2star.org/islux/_HnGo/index-
11.htm

From what I've heard Hikaru no Go is entirely CG 
done, as Studio Pierrot no longer uses cels (the 
new FY OVA is also CG done, as well as Saiyuki). 
So far I have seen repros of Hikaru, Sai and 
Akira.