Animation Cel

A "cel" is a transparent celluloid sheet where drawings are painted usually by hand. Several "cels" comprise an animated sequence, that is later photographed, developed, edited, added sound, and finally shown on TV or at cinemas as an animated serie or movie.
I found by accident that real production "cels" are sold on eBay. Here are some examples: one is from Gatchaman and the other one is from the Robotech animated series:



Both are for sale right now at eBay, "cels" go from US$20/US$30 to over US$500 (The Robotech one is for sale right now at US$250).
There's no doubt "animation cels" are real collector items, I wish I have one of those some time in the near future.

Links:

http://en.wikipedia.org/wiki/Cel
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=220413388128
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=380123095374