Question: Every time I go to a casino, I notice that some of the older slot machines that I used to love to play have disappeared. Older models seem to slowly fade away, casino by casino, until you simply can't find them any more. But where do these old slot machines actually go, and why do some machine disappear so quickly while others seem to stick around forever?

Anyone who regularly visits a casino knows that slot machines are changing all the time; fancy new machines are rolled in while old favorites are quietly removed from the floor and disappear from view. The reasons behind which machines stay on the floor for years and which ones are taken away in the middle of the night are simple – it boils down to the individual machine's performance.

Like all other casino games, slot machines serve one single purpose, to make the casino money. Casinos monitor each machine and evaluate its performance based on how much money is wagered on it each day, and the total amount of cash taken in by that machine during the day. So if a machine is either not popular enough to reach a decent daily wagering amount, or if it simply doesn't take in enough money to be profitable, it's time to get rid of it and make way for a machine which is.

While many people adore the romantic old 'one-armed bandits' of the 1950s, or feel nostalgic towards the 3-reel Bally or IGT slots of the 1970s, the reality for the casinos is that these machines simply can't take in enough money to keep up with modern video slots. Older machines have mechanical and technological limitations which prevent them from being able to take in, or pay out enough money to keep modern gamblers happy.

For instance, the first ever slot machine, The Liberty Bell, was invented in 1895 as a way of entertaining San Francisco saloon customers. Lining up three Liberty Bells was enough to pay out the big jackpot: 10 nickels, or $0.50. While the machine is a historic classic, which you can still see in the Nevada State Museum, a modern machine that only pays out 10 nickels wouldn't last a week on the casino floor.

The same goes for the 3-reel slots of the 50s, 60s, and 70s. Slot machines in the 40s and 50s were only able to accept one coin at a time, and consequently were only able to pay out a certain maximum jackpot. These gorgeous classics were rendered obsolete by the 1970s, when multiple-coin machines with automatic hoppers were able to increase the potential jackpots, along with the casino's potential take, ten-fold.

The video and progressive slots of the 80s and 90s were another huge step forward in profitability for casinos. Linked progressive jackpot machines, which promise the possibility of winning millions of dollars in a single spin suddenly made machines with $1,000 less interesting. The ability of modern video slots to accept and dispense tickets and do away with coins completely has even further diminished the profitability of older, mechanical-reeled machines.

Sadly, many of the beautiful, much-loved slot machines of yesterday are no longer with us. Casinos want to squeeze as much out of a slot machine as they can, so many old slot machines which have been removed from the casino floor are sent off to the workshop to be dismantled and used for parts, or otherwise sold as scrap.

But not all slot machines end their lives on the scrap heap, others are simply locked away in the basement of the casino, in eerie cemeteries of bars, cherries, bells, and triple 7s. Sometimes casinos sell older machines to other businesses, such as Nevada gas stations hoping to supplement their revenue while people fill their tanks.

Old slot machines can also be sold to private collectors or other businesses. In places like Nevada, these machines can be sold in perfectly working order. In other places, they must be rendered inoperable, or at least unable to accept and dispense money. There are plenty of shops based in Nevada (as well as Atlantic City) which deal in old slot machines, either in person or over the internet. In the United States, most states allow you to own a slot machine as long as it is more than 25 years old and is unable to be used for gambling. So even if you favorite slot machine is no longer in casinos, you might be able to have one in your living room.