You might have hoped you'd heard the last of this topic. However, a discussion with David Gale has inspired the following vicious conundrum. Consider a transparent sheet of overhead projector film, onto which has been glued the legend "P A B L / N H Ø O" in plastic symbols, coloured green on the front and red on the back [from a numerate classicist toddler's alphabet: there would have been 10 symbols, but the swastika's been eaten]. Flatten it out on the table [the sheet, not the toddler], with the lettering legible, and coloured green. Let's call this positively oriented. Now turn it over, as a page from a book, and slide it back again. It occupies the same space as before; and the legend is illegible and coloured red. The orientation of the sheet is now negative. Then begin again, but instead lay it against a mirror. The image again occupies the same space (more or less) as the original. The legend in the reflected image is legible and coloured red [or if you foozled it, illegible and coloured green --- whichever]. Question: is the reflected orientation positive, or is it negative? If anyone comes across a previous reference to something related, I should like to hear about it. [Martin Gardner's "The Ambidextrous Universe" might perhaps be a good place to start looking.] Fred Lunnon