on the magnetic strip (magstripe) on the back of most cards, be they credit cards, bank cards, slot cards, phone cards, gift cards, etc.

It is a number, usually a long one and usually written in hexidecimal. It is the computer system at the distant end of each reader (the slot card recepticle, the ATM machine, the cash register credit card swipe device, etc.) that maintains the information about who and what that number is about. Nearly all the devices that we daily swipe cards through are readers only, i.e., they can not write new data to a card.

Can that number written to your friend's card be read and copied by another device? Yes. Can that number then be written to another card? Yes.

But there is no difference between having a copy of the card than having the real card. It only contains a number, and no data per se.

When dealing with magstripe cards, data (the number) can be written to one of four different tracks, although track 2 is the most common. Readers, in order to read the number must have the read head aligned with track 2, or what ever track it is intended to read. BTW-This term track goes back to the old 4-track and 8-track days of tape players. Anyway.....

Although there are exceptions, I would say that the vast majority of magstripe cards in-use for slot club play contain only a number on the card.

For several hundred dollars you can buy an encoder that both reads and writes to a magstripe card. If you were so inclined, you could erase the data on your Mastercard and re-code it with your slot club card data. Imagine the looks you would get from fellow players inserting a charge card into the reader! Of course you could also have a custom design printed to a card and then encode that card with your casino card data and use it.

A little complicated, sure, but can it be done, sure!

Jim Follis