I was idly flipping through some cel sites, and 
randomly wondered how dealers manage to keep 
track of cels for so many series.

I know for the private collectors, it's rather 
easy to price their own cels for sale, because 
usually they're from only a few series.  But for 
dealers who sell cels from 50  series, I'm often 
amazed at the fair pricing of the cels.

So my question is, how do you keep track of the 
important scenes/characters from so many anime?