Case ye, case ye; on with your vizards: there 's money of the king's coming down the hill; 'tis going to the king's exchequer. (2.2.1)
It's no coincidence that Hal and his rebellious cronies rob the king's exchequer at Gads Hill. The robbery of the king's treasury (during which time the thieves steal coins called "crowns") is meant to parallel the rebels' plot to steal the king's crown and power. Shakespeare uses this kind of doubling technique throughout the play to connect the two plots and also, perhaps, to shed a comic light on the Percy family's uprising.