I think sufficient time has passed for this not to be sensitive (or useful) info anymore, so here's how you could empty an indiana jones holy grail due to a programming flaw, we had literally a day to find one and do it when the info was given to us, found 4, 2 were switched off, one had an engineer working on it and re chipping it (updating the software and fixing the hole) but the last one was turned on, and full, once in a life time stuff, nice when it works out tho.
http://www.youtube.com/watch?v=4JmMNrlHgKI
I suppose it could be seen as morally wrong to do that, but legally speaking it isnt, as unless you are obtaining credits via deception/fraud (tampering with note acceptors) or forcibly breaking into the machine (tooling) then pulling an emptier is not a crime, as its classed as nothing more than exploiting a glitch in the software, but it will of course result in a barring (and a good kicking depending what pub youre in) if you get caught, luckily we didnt.
And how was it possible, heres the science bit
Play it on £1 a go, but only put in one pound at a time because if there are credits left in it then it wont work.
So yeah, play on buck stake until it gives a GATW (Go All The Way) machine flashes, music plays to tell you its a guaranteed jackpot board, plus is says GO ALL THE WAY! on the display, so keep pressing start and it will go all the way to jackpot.
Then you collect the £70 out, the bank needs to be empty, but alas, there are no credits left in the machine to do the repeat chance, but this is good, this is what you need in order for this to work.
Press change stake, until you are on 25p a play, then put exactly 25p in and the repeat chance will take place, it usually shows that its giving you another 10 or 15 quid, but it doesnt, eventhough you keep landing on cash amounts, you dont actually get it, but this does not matter.
Change back to £1 stake and play 1 pound coin in at a time as before, and then the next board will be a GATW again, as the combination of running out of credits, changing stake, running out of credits on 25p stake and then changing back to buck stake, plus clearing the bank out before any stake changing somehow made the machine 'forget' it had paid out, it did not register the win, and therefore is still gagging to pay out, every board will be a GATW until you stop it by either or not changing stake, or leaving credits in it, literally repeat until as near to empty as you dare leave it.
Knowing how much these machines hold when full (£350) and knowing how much is in the machine already is a must, as you do not want to IOU the unit, so if you can hear its full (coins are dropping to the bottom because the hopper is full) then you know exactly how many times you can do it before it runs out of money, which you do NOT want to do, not good, as it attracts attention.
So yeah, thats how it was possible, but as you would expect, once the manufacturers got wind of xxx amounts of units running out of money, it was a high priority update to fix the flaw, so 1 or 2 days max to find one before they were either turned off, re chipped,or removed from the premises completely, youll never find an unchipped one now.