A mate who used to be in the Navy years ago told me about a gag that he called the Sailors' Breathalyser. He described it as a brass tube with a propeller attached, the idea being that you challenge someone to blow down the tube to make the propeller spin round. When you demonstrate it, you secretly keep your finger over a hole somewhere on the tube. When it's given to someone else to try, they get covered in soot or talcum powder that blows out when the hole isn't covered. I'm trying to get hold of one for a present. Anyone know where I could buy one? Anybody heard of it before?? Cheers!