I could see where it would be dishonest not to 
mention that the cel was restored when reselling 
it. That is important to many people. To others 
it may not matter so much, as long as it was done 
properly and looks just as beautiful. I don't 
really know whether the value of the cel would go 
up or down with restoration. It probably depends 
on how bad the damage was and how well it was 
restored. Personally, I would not base the 
decision on whether to restore or not on 
potential monetary value, but on how badly I 
would like to see it returned to its original 
beauty.