Bitcoin's proof-of-work problem is solved in constant time, since there is no asymptotics. Complexity classes are irrelevant here.

Complexity class of an idealised version of Bitcoin's proof-of-work (hashcash)?
I'm trying to find an alternative to the standard tombstone qed symbol for more informal papers.
I initially thought of an empty square with Pub written inside, but what would actually be better would be a small beer mug symbol. (much like the one found in this set of icons http://dutchicon.com/iconsets/food-and-drinks-icons)

Unfortunately there doesn't seem to such a symbol in the comprehensive latex symbol list (although many funny symbols can be found there).
Has anyone thought about this? Is there any quick-and-dirty solution?
