TIL about Lehmer codes... and "poker encoding" ;)

(I just prefer poker to solitaire...)

Someone else mentioned that the orientation of the cards (up or down) and possibly even the front-back facingness of the card (facing up, facing down) would add another 2 possible bits to the available encoding space. (Of course, at that point you'd have to also encode which side of the whole deck is the "top"...)

My own thought was to add par2 to make it robust against small errors... at the cost of some transmission space!