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In cartoons, you often see characters like Scrooge McDuck with a coin where they have drilled a hole in the middle and attached a string, enabling them to insert the coin multiple times and keep pulling it out from the machine repeatedly, tricking the machine into believing that many different coins have been inserted.

Is or was this actually ever possible? I was too honest and scared to ever try this as a kid, although I did think about it many times. If I had the resources, I would probably at least have tried it once, just to see if it would work.

Maybe they had predicted this and implemented some kind of scissors auto-cutting above the coin every time it registers a new coin? Or maybe the coin moves in such a way that any string would get stuck or not be able to pull it back up again?

If this was actually possible, did some people actually do it? I almost never got to play on the arcade games, because I had so little money, so it would've been a game changer (literally) to me. On the other hand, doing it on slot machines and other gambling devices seems very illegal, since you'd actually be robbing the one-armed bandits!

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    While this normally didn't work because of the latching occipita mentioned one thing that did work with a lot of old arcade / vending machines was discharging static onto the coin slot. They were all metal and I guess the low-voltage switches didn't have enough dielectric strength to withstand it so it'd trigger a credit.
    – PeterJ
    Dec 17, 2020 at 13:50
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    @another-dave, this looks like a question about retro gaming hardware. You might want to take a look at retrocomputing.stackexchange.com/help/on-topic to see what is considered a question about retrocomputing.
    – Algimantas
    Dec 17, 2020 at 18:27
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    Sure, but c'mon - there's no "computing" content in dangling a coin on a string. I'm pretty sure the intent of allowing retro gaming hardware in the retrocomputing forum is for the computing content.
    – another-dave
    Dec 17, 2020 at 18:51
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    @another-dave The dangling per se doesn't involve computing, but how the machines recognized the proper number of coins of the proper denomination (and thus how they could be fooled) could be considered "computing" in the electromechanical sense. No, there isn't any digital logic involved, but my understanding is that isn't a requirement for this Slack.
    – R.M.
    Dec 17, 2020 at 19:12
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    It did feature in the first episode of Halt and Catch Fire (which is retro and which rocks) so +1.
    – Alex Hajnal
    Dec 17, 2020 at 23:09

11 Answers 11

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I actually did this with pinball machines in 1980-ish. Getting 3-5 games before the coin was lost wasn't impossible, and some of my friends did better than that.

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    This answer could be improved by more discussion of which pinball machines they were (do you remember the machines' names?), and, if possible, the details of the coin counting mechanism they employed which made them susceptible to this trick.
    – R.M.
    Dec 17, 2020 at 19:14
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    At the college I attended in the ‘80s, we had several standing arcade machines in the student lounge. Among them were Battlezone, MissleCommand, and Tempest. At least one of them (forgot) would accept a coin tossed up into the bottom of the coin return and then return the coin. I’m not certain if one of the other students had tampered with the thing though. This was discovered after a couple of weeks and the machine was removed.
    – Michael Tracy
    Dec 19, 2020 at 13:38
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    Another mechanical technique (sorry, I don't remember what games this worked with) was a swift kick on the front of the machine. Placed right, it would ring up three games, just as if you had put in a quarter. Even if it tilted one out, you still had two free games. But that took a toll on the machine...
    – Pete Becker
    Dec 19, 2020 at 14:39
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It's difficult to be sure that there was never a system in use that was vulnerable to this trick, but certainly there were systems available from a very early stage that weren't. This coin acceptor is typical: it uses a ratchet mechanism that engages the moment the coin is accepted to prevent reverse motion.

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    But most arcade machines I've seen don't use that sort of coin slot. I usually see them on pool tables.
    – BlueRaja - Danny Pflughoeft
    Dec 17, 2020 at 19:13
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You could fool purely mechanical devices with mechanical tricks. One trick I have used when a kid, was with bottle caps. We wore them out underneath our shoes, until they were the size of a coin, fit for a bubblegum machine.

But I get the feeling that with the earliest introduction of electronics into slot and arcade machines, the electronic sensing of the correct coins was not far behind in development.

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    It wasn't even always electronic. Stick a magnet next to the coin ramp, and induced currents in the coin will slow it by a varying amount depending on the alloy. Coins moving too slow or too fast will simply fall into the coin return slot, while ones moving at the right speed will trigger the acceptance mechanism.
    – Mark
    Dec 17, 2020 at 22:30
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    Bottle caps? So Fallout :)
    – rackandboneman
    Dec 18, 2020 at 3:08
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    @Phoenix Electrical - perhaps electro-mechanic - but electronics is a term usually reserved for something using active components like amplifiers &c... From Merriam-Webster: "a branch of physics that deals with the emission, behavior, and effects of electrons (as in electron tubes and transistors) and with electronic devices"
    – Baard Kopperud
    Dec 18, 2020 at 9:56
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    @Mark US coins at least are not magnetic (with the rare exception of 1943 steel pennies). This might work in Canada, where the coins (nickels, dimes and quarters at least) are magnetic. A few other countries also use coins that are magnetic, but most don't.
    – Darrel Hoffman
    Dec 18, 2020 at 15:25
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    Coins don't need to be ferromagnetic to be slowed by magnets. Any conductive material will have a current induced when passing through a magnetic field, which then creates a magnetic field of its own that will oppose the motion. Just google magnet+copper pipe.
    – AI0867
    Dec 18, 2020 at 17:45
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I can personally confirm this worked on at least some video arcade machines in the 80s, when I was young. I can vividly remember being at an arcade at one point, and losing a quarter in the machine. Instead of refunding my money, the attendant came by and gave me a free game with the use of a coin-shaped slug welded to a long, flexible wire. It looked like an official tool-of-the-trade, not something jury-rigged or hand-built.

It clearly made a big impression on me, given that was over thirty years ago.

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  • I've seen tool shaped like a flat spoon used for this.
    – Jasen
    Dec 20, 2020 at 5:56
  • I tried to do an image search, but couldn't figure out the right terms to use. I'm guessing there's some in-industry term for this.
    – Chris Sunami
    Dec 21, 2020 at 14:13
  • oh man. your description is amazing. your "welded wire onto quarter" is like the scotch tape trick but on steroids (see my answer below).
    – Trevor Boyd Smith
    Dec 21, 2020 at 16:08
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The answer is yes, in some cases....

Back in the 80's my college roommate figured out how to defeat the coin operated washing machines at the local laundromat. The machine took US quarters. It had the type of coin receiver where you loaded several quarters into slots on a metal plate, then pushed the plate in and pulled it out. The machine took the coins, and the washer started.

He discovered if he used Canadian quarters AND pushed the plate in and retracted it quickly the washer would start and the Canadian quarters would still be on the plate. This only worked with Canadian quarters. It was not 100 percent effective as the washer would get 1 out of every ten or twenty quarters. Also, the coin mechanisms were not worn out and the trick worked on all of the 20 washers. The washer always got the US quarters. He washed his laundry at low cost for years. The driers were different and couldn't be beaten. Also, there was an air hockey table at an arcade where a similar trick worked 3/4 of the time.

On old gum machines that took dimes you could put your dime in, spin the handle real fast, and get your dime back as well as a big gumball. That worked about half the time.

Both examples are in the spirit of the original question which is can you get the service and get your coin back. I point out that doing this intentionally is theft even if the machines let you.

It is hard to design things that are perfect. If one person in 1000 gets a free wash it will cost more to fix the problem than is being lost.

Casinos are a whole different matter. They are always watching and if the slot machines can be scammed they will catch on and fix them. The roommate mentioned above above was from Vegas. Back in the early 80's he would dare to try to cheat a Vegas slot machine.

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    I remember from the same era someone rigging something to defeat those washers with a coat hanger and masking tap, but I don't really remember how she did it.
    – Gort the Robot
    Dec 17, 2020 at 23:47
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    +1 for "I point out that doing this intentionally is theft even if the machines let you.". This thread is an interesting read about past creative misdeeds, but no one should attempt them today, as they are fundamentally theft (if petty theft).
    – bob
    Dec 18, 2020 at 16:16
  • I've found a gumball machine that probably had a broken back plate in the gumball dispenser that let me lift up the latch on the coin lock mechanism. I was able to turn the slot without any coin. I took 1 and realize it is theft so I bought one and never touched that machine again.
    – Nelson
    Dec 19, 2020 at 7:33
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In the early days, some pay-phones were modified because it was possible to recover the coin (push button A), once a connection had been made.

The other common device was to use slugs (like washers or coins of lower value), to get the games at discount prices. This is one of the reasons for having different-sized coins for different denominations and countries.

For example, NZ money was worth $1NZ = 80c AU, but their coins were the same size for 5-20 c. So feeding a 10c NZ money gives a game for 8c.

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    Some decades ago, some college friends told me there was a low-value Israeli coin with similar size/mass to the US quarter and could be used in video games...
    – Jon Custer
    Dec 17, 2020 at 14:34
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    The UK 10p and 5p coins were reduced in size because they conflicted with the german mark, etc. People were using one-mark coins as slugs against the 5p.
    – wendy.krieger
    Dec 17, 2020 at 14:36
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    When I was in college, in the early 80's, I was aware that Connecticut (a state in the US) had public highway toll tokens that were the size of a US quarter, and fit in parking meters. Not that I ever had a friend who lived there bring me a roll now and then. I'd never have done that.
    – JTP - Apologise to Monica
    Dec 17, 2020 at 21:32
  • Also when I moved back to NZ recently I had a lot of old NZ coins which were no longer legal tender - but some of the parking meters in Auckland hadn't been reprogrammed to reject them ;)
    – David Waterworth
    Dec 17, 2020 at 22:19
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    @wendy.krieger wasn't 1 mark worth more than 5p?
    – Eric Duminil
    Dec 18, 2020 at 0:32
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Not a gaming machine, but a street phone operated by coins. Pretty much working trick in '80s in USSR and "influenced" countries (I think there was only one model of a street phone).

The trick worked for a while (years), then rather strong inflation kicked in and the trick became pointless.

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There was some washing machines that were susceptible to a modified "quarter on a string" trick. These washing machines were circa 2002-2004.

Given that the above mentioned "coin on a string trick" worked in 2002-2004, the example shows that some coin slots could be tricked (and these machines were not old)!

I think coin slots are probably like locks and have a large variety with some being very cheap and some being more expensive (probably casino slot machines you can not trick).

long story:

  • Eventually the washing machines switched to a card based system
  • the card held the amount of money (less people cheating, less maintenance, less labor collecting coins, less broken machines caused by people jamming the coin slot)

The "modified" version of "quarter on a string was to use "many layers of scotch tape" (i won't go into detail on purpose).

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    Though if the card merely contains a readout of the balance (perhaps lightly encoded in some way), then any yahoo with a magstripe reader/writer and a serial port could do the high-tech version of the "coin on a string" trick.
    – Sebastian Lenartowicz
    Dec 18, 2020 at 17:30
  • @SebastianLenartowicz perhaps you are correct but that sort of discussion is out of scope to the question/answer. (fun story: i heard a story of a sales guy who sold test-equipment. he happened to have a recorder and transmitter. so for fun one day he recorded his neighbors garage clicker then played it back as a joke with great amusement. test-equipment was probably wild-guess $100k to $300k).
    – Trevor Boyd Smith
    Dec 21, 2020 at 16:04
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Not for a coin on a string, but there is (and probably several) cases of 'bill on a string'. https://www.indystar.com/story/news/crime/2019/05/24/bill-string-car-wash-theft-suspect-faces-new-charges-after-chase/1204906001/

This was not the one I remembered, but similar to. A laminated bill and a long spool of plastic were fed into the machine. When refunded, the whole amount were pulled back out.

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Until the 1990s, pay phones in Israel used asimonim, tokens with a hole in the middle. I was told in the 1970s by Israeli kids that the string trick worked on many pay phones.

image of asimonim, Israeli phone tokens with a hole in the middle

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It was possible to use a length of plastic strimmer* line permanently set into a v-shape at the end by melting a section, on some 80s machines.

  • US: Weed Whacker
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