From Peppermill Wiki
Style 831 is an odd peppermill -- the contours match nearly exactly those of Mushroom Disguise, but Style 831 has a perfect mirrored lip on its lower half, right below the seam. It is possible that the two peppermills are the same, one is just a design evolution of the other. If that is the case, Mushroom Disguise would be the final design, since examples of this mill have only been seen from a limited manufacturing period when the unmarked Tre Spade grinder was used. Scratch that. These mills appeared in material at the same time, so they couldn't have been versions of each other.
