ask the seller what the sketches consist of, and 
if the cel layers match those sketches (douga?, 
genga? which ones?)  Chances are, if the cel is 
repro, it should be just one layer.  Pierrot has 
sold that particular repro in their Saiyuki 
events and online shop. For a "hanken" that's 
made exclusively for magazine use, I doubt they'd 
use the same sketches used in CG production  
(image, and moving mouth, etc).  
Remember that Pierrot sold repros, and later sold 
genga/dougas. It's just too convenient for the 
certain people to just match the genga/douga they 
got with the already available repro, and then 
there you go, a match!  and call it "hanken".  Of 
course, this would be a worse case scenario (^^;   
All in all, you just have to ask the seller, and 
maybe the seller can ask their provider.  And 
hopefully the provider is knowledgeable enough of 
not confusing with any ready reproduction cel 
whose image were shown on magazines as "hanken".  
Some people have this misconception.