key

This is also another helpful resource on cel terminology:


http://www.fukushuu.org/cels/celfaq.php?g=y
http://www.fukushuu.org/cels/faqsection.php?g=c&ft=3
http://www.fukushuu.org/cels/faqimageindex.php?g=c

It's always a pleasure when you reunite a sketch with a cel and find out the cel is actually a key one. ^_^ I find that often key cels aren't marked and it's only on the sketch that the number is circled.