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Ask the Slot Expert: Do Casinos Mark Money with a Pen?

13 February 2013

By John Robison, Slot Expert™

You responded to "Do Casinos Mark Their Money" with a resounding "no". However, I was in AC last week and the craps table dealers were putting a stroke on the incoming bills (probably $100) with a pen leaving an invisible mark. This was the first time I saw this so maybe there have been some changes. I know this is not related to players handling money in slots. Comments?


Dear Fred,

The dealers were not marking the money. They were checking it to make sure it was not counterfeit.

The pens contain an iodine solution that reacts with the starch in wood-based paper to leave a black mark. Genuine currency is printed on linen. The solution does not leave a mark on linen.

You can buy your own currency validation pen from an office supply store.

Jackpots for all,


There seems to be a rash of new video poker games that require six credits per hand for the maximum payoff. My computer training program does not have this option in calculating the percentage of the game payback. Will dividing the calculated 5-coin payback by 5/6 give the correct result? Are there any new training programs that offer the 6-coin feature?

Second question: You have mentioned several times about "time on device programming". It has always been in reference to slot machines, but very often it seems to apply to video poker machines. At least that's my perception. At a particular casino I was playing a quarter, full-pay JOB game. A twenty-dollar bill would soon be wittled down to five dollars. Suddenly at that level, winning hands would appear and move the credit meter to ten dollars or so. It's probably just my imagination? But just inserting five dollars and cashing out any winning amount resulted in a plethora of tickets, but a profit. So is it possible to program a video poker game for "time on device"?

First answer: I checked Wolf Video Poker and Video Poker for Winners and neither have been enhanced to handle 6-coin machines. To calculate the long-term payback for the paytable, enter 5/6 of the 6-coin payout into the 5-coin payout column and calculate the long-term payback when playing five coins at a time. Another option is to enter 1/6 the 6-coin payout in the 1-coin payout column and calculate when playing one coin at a time.

Second answer: I don't think I ever used the phrase "time on device programming." It would be illegal in the United States to start paying off once you were about to run out of credits to give you more time on the device. The result of each spin or hand must be determined at random without any regard for what has happened in the past and without any external influence, like how much money the player has on the credit meter.

Machines with higher hit frequencies tend to give players more time on device. There is no programming involved. Video slots usually have their reels laid out so they have many small payouts. On Jacks or Better, the high hit frequency is just a consequence of the game itself. We frequently hit the lower-paying hands.

Jackpots for all,

John Robison
John Robison is an expert on slot machines and how to play them. John is a slot and video poker columnist and has written for many of gaming’s leading publications. He holds a master's degree in computer science from the prestigious Stevens Institute of Technology.

You may hear John give his slot and video poker tips live on The Good Times Show, hosted by Rudi Schiffer and Mike Schiffer, which is broadcast from Memphis on KXIQ 1180AM Friday afternoon from from 2PM to 5PM Central Time. John is on the show from 4:30 to 5. You can listen to archives of the show on the web anytime.

Books by John Robison:

The Slot Expert's Guide to Playing Slots