I did a quick check on ebay for hones (I need a few more to finish tiling my basement) and came across an interesting Escher. I remember a few months ago Chrisl mentioning that he found a barber hone with grooves in it that he could only imagine was from breadknifing. Well, I'm guessing that this Escher is a slightly more extreme example of somebody doing a heck of a lot of breadknifing!