I just bought a few of these so that I could look at them in person. I'll have to do a little research to see if there are any tell-tale signs that these are truly IB cels, which I hope they are.

http://www.ebay.com/itm/RARE-2-x-35mm-Film-Cells-Vintage-Star-Wars-1977-Han-Luke-amp-Leia-/121584354755?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2047675.l2557&nma=true&si=LI91UZJ%252FBqkf9DhZBqBTEwI8vX8%253D&orig_cvip=true&rt=nc#ht_418wt_0

Offhand, does anyone know of a fairly easy way to determine if these are IB cels as opposed to photochemical? I imagine the "emulsion" side of the film would look different (?)