For every girl who's sick of explaining it to her boyfriend...

The football coin – half a million of which are now in circulation – shows a midfielder about to pass to one of two team-mates [Where?? Where's the effing midfielder??], with the first player, on the left, marked as offside, and the second, level with the defender, not offside. But the diagram appears to illustrate the offside law as it was until 1995, when it was overhauled by the International FA Board to reduce the number of stoppages in matches.

The revision to the law meant that any player in an offside position when the ball is played is no longer automatically penalised. It states: "It is not an offence in itself to be in an offside position."

Instead, for the past 17 years assistant referees have been told to wait and see whether a player in an offside position becomes involved in active play, either by "interfering with play, or interfering with an opponent, or by gaining an advantage by being in that position". That means that if the midfielder on the coin passes to the striker on his left, but the striker chooses not to play the ball or interfere with an opponent, he is not offside and play continues.*

The Royal Mint says the coin was designed "to provoke discussion", but the Referees' Association member Mal Davies, who works with the former head of Premier League referees Keith Hackett on the Observer's long-running You are the Ref feature, said using such old information was "embarrassing".