#

In the US, it's usually referred to as the pound sign. We don't have to worry about the British pound. This matter has been discussed in some detail before: http://wordsmith.org/board/showthreaded.pl?Cat=&Board=words&Number=99.

By the way, I assume the English measuring system was still in use at the same time as the current British currency system. You say it's confusing to call # the pound sign, but wouldn't it be much more confusing to have weight and money have the same name, especially when a pound doesn't weigh a pound?