Jimmy administers the barrel activity in the Warriors' Guild, in which you carry barrels on your head for tokens. His record is four and the player can beat him by balancing five. Since he can't give tokens himself, he copies a signature for the player to give to someone who can. This is probably because he is slightly intoxicated.
When talking to him after While Guthix Sleeps, he will still mention that Sloane can give players the tokens they gained from balancing kegs on their head. He does not know that Sloane is dead.