The lines are too rough to have been used for the 
cel, so it's probably a genga. Now the question 
is, what sort of genga is it? 
Check out Brian's animation guide or Ash's site --
 links on cel.org -- for more information. They 
go into some detail about different types of 
pencil sketches, and how to distinguish them from 
one another. 
Good luck on your auction and get well soon!