Fascinating - I don't remember ever seeing that usage, didn't know it's used for pounds/weight, although I knew "pound sign" is one name for #. Seems the sign evolved from "lb" with a horizontal line through it.
"When # is after a number, it is read as "pound" or "pounds", meaning the unit of weight. ...rare outside North America."
Sorry to go even more OT, but were you familiar with the "soaking wet" part? Your profile says Australia and I'm curious if that's an idiom there as well.