Hmm, in my opinion if a cel is taken from the 
series itself and used in the opening later on, 
then it really can't be labeled as an OP cel.  I 
am a big Kenshin fan, and recognize this cel 
from the show.  If a cel is originally in the 
show, then used as an OP or Ending credits cel, 
it should still be classified as just a normal 
production cel.  

Without getting into other issues, the main one 
is that the quality is less than what OP cels 
usually are.  This especially rings true with 
Kenshin cels, as the OP cels are some of the 
most beautiful, while cels in the show can be 
rather sloppy some times.  (sorry Kenshin 
creators and fans, please don't kill me for 
sayint that!)