I have three cels that do this, one from Maho 
Tsuki Tai (feel free to die laughing at my 
spelling ^_^) and two from Vampire Miyu OVA. None 
of these cels seemed to show line damage under 
the "correction layer" and none of the additional 
layers looked to be done by some other collector. 
So it was probably done at the studio for 
purposes of appearance.

Many Sharp Smiles,
--Drac