Color Test/Model Cels

These are generally a very simple cel of just a character to show what colors should be used by the painters when they are painting the cels.  Model/Color Test Cels are very specific to pre 2001 animation, as with the modern Settei sheets will come with something called a color reference that basically does the same thing but is in reference to the colors painted in digitally.  Their rarity depends on the series for this, there seem to be a lot of test cels from both CCS and x/1999 that I have seen.