BTW, the answer to Belbo's riddle: Do you have the password?
The answer? "No."
Personally, I think Eco may have cribbed a bit from Tolkien (recall Frodo's solution to the password needed to enter the mountains, which the great Gandalf could not solve).
The point is that sometimes we may be a wee bit too smart for our own good when it comes to solving riddles.
Here we are, sharpening sticks amongst ourselves rather than going straight to the source and asking, say, Kodak to finally spill. Out with it, Rochester: What's the diff between films? Where does the silver halide end and the iodide and sensitizing dyes begin?
Oh, I forgot...Kodak is all ones and zeroes these days.