# Those 7-Sided UK 50 Pence Coins **URL:** \ **Category:** Factual Questions\ **Created:** [January 9, 2010, 8:13pm UTC](https://boards.straightdope.com/t/those-7-sided-uk-50-pence-coins/524317 "2010-01-09T20:13:39Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![jjimm](https://avatars.discourse-cdn.com/v4/letter/j/ba8739/32.png) [@jjimm](https://boards.straightdope.com/u/jjimm)\ **Post date:** [January 9, 2010, 10:22pm UTC](https://boards.straightdope.com/t/those-7-sided-uk-50-pence-coins/524317/21 "2010-01-09T22:22:49Z")
> [@Mangetout](#): > > The UK 50p and 20p coins are both curves of constant width - that is, each side is an arc centred on the opposite corner - this helps them not to jam in any chutes or channels in vending machines or other coin mechanisms. (and the coin measures the same diameter no matter which way it falls through) > > [Curve of constant width - Wikipedia](http://en.wikipedia.org/wiki/Curve_of_constant_width) Blimey, I did not know this. Again, **Mangetout** , your value-added knowledge of things unanswered never ceases to enlighten. Cheers! 😃 Am I allowed also to say something about the arguments that say adapting vending machines as the reason dollar coins in the US wouldn’t work is clearly bunk? Or is that wrong for GQ? PS, **ralph** , if the 50p annoys you, check out the Cook Islands’ [triangular $2 coin](http://www.mattwardman.com/blog/wp-content/uploads/20071207-triangular-coin-cook-islands-1992.jpg) to really give you an aneurism. (Though my personal fave from there is the one with [the guy with his cock out](http://farm3.static.flickr.com/2113/2430818604_6a9dfbf2e3.jpg).) ---
**Author:** ![Ximenean](https://avatars.discourse-cdn.com/v4/letter/x/aca169/32.png) [@Ximenean](https://boards.straightdope.com/u/Ximenean)\ **Post date:** [January 9, 2010, 10:39pm UTC](https://boards.straightdope.com/t/those-7-sided-uk-50-pence-coins/524317/22 "2010-01-09T22:39:32Z")
I appreciate that a question might set off interesting tangential discussions, and I agree that this forum is not just about answering factual questions in a dry, encyclopaedic manner. I myself have been upbraided with answers such as “dude, just Google it” in response to threads I have started here. It’s just that there are a few posters who continually make posts which suggest that they simply can’t be bothered to look things up themselves, or perhaps that they just can’t stop posting. That is what prompted my admittedly snarky initial repsonse. ---
**Author:** ![Lobsang](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lobsang/32/4067_2.png) [@Lobsang](https://boards.straightdope.com/u/Lobsang)\ **Post date:** [January 9, 2010, 11:01pm UTC](https://boards.straightdope.com/t/those-7-sided-uk-50-pence-coins/524317/23 "2010-01-09T23:01:22Z")
I can see your point. And I am not trying to perpetuate the argument here, but I thought of an analogy of ‘dude, google it’. It’s a bit like saying “Dude, buy a watch” to someone who asks the time… …Which, if I think about it, is something I might actually be tempted to say to people if I wasn’t a scaredycat about the need to be civil. I went to the effort of buying/wearing a watch so that I could tell the time for myself. I didn’t do it so that I could be the announcer of time. (Just the Thief of Time) ---
**Author:** ![Celyn](https://avatars.discourse-cdn.com/v4/letter/c/9dc877/32.png) [@Celyn](https://boards.straightdope.com/u/Celyn)\ **Post date:** [January 10, 2010, 1:37am UTC](https://boards.straightdope.com/t/those-7-sided-uk-50-pence-coins/524317/24 "2010-01-10T01:37:58Z")
When the 50 pence coins first appeared, there were people who complained that it was all wrong, and coins must be round, dammit, and that the sharp edges would cause tears\* in people’s pockets, and what the hell was ever wrong with a proper ten shilling-note anyway? (History does not relate, but I imagine this was a delightful chance for these people to have conversations that did not entirely consist of complaining about the weather not being as good as when they were young. ) Now I think of it, I suppose there would have been difficulty with vending machines **at first** , but pretty soon they all caught on, given that vending machine proprietors are in the business of wanting to take money. I have had annoyances with vending machines that want a pound but can’t cope with a pound note, however. \*That’s “tears” as in rips in the fabric: it’s the lack of coins that cause the tears as in weeping, of course. ---
**Author:** ![TBG](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@TBG](https://boards.straightdope.com/u/TBG)\ **Post date:** [January 10, 2010, 6:43am UTC](https://boards.straightdope.com/t/those-7-sided-uk-50-pence-coins/524317/25 "2010-01-10T06:43:24Z")
It’s also easier to hit the back button in your browser if you feel a question is beneath the board than post a “use google and wiki” post, isn’t it? I didn’t even know UK had 7 sided coins. Now I do. Ignorance -1. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [January 10, 2010, 8:23am UTC](https://boards.straightdope.com/t/those-7-sided-uk-50-pence-coins/524317/26 "2010-01-10T08:23:48Z")
Since decimalisation, the size of the 50p coin has been revised - it used to be much larger - the same is true of the 10p and 5p coins, as well as most of the banknotes. The 20p, £1 and £2 coins, which were new introductions, appearing some time after decimalisation anyway. In each of these cases, manufacturers of coin-operated machinery coped quite well with the changes - for a couple of weeks or months there might have been labels on some machines saying “this machine does not accept the new [whatever] coin”, until the adaptations were made. I think coin mechs are discrete modules in most coin-operated machines nowadays, making them quite easy to swap out. ---
**Author:** ![gaffa](https://avatars.discourse-cdn.com/v4/letter/g/e68b1a/32.png) [@gaffa](https://boards.straightdope.com/u/gaffa)\ **Post date:** [January 10, 2010, 10:00am UTC](https://boards.straightdope.com/t/those-7-sided-uk-50-pence-coins/524317/27 "2010-01-10T10:00:33Z")
> [@Mangetout](#): > > In each of these cases, manufacturers of coin-operated machinery coped quite well with the changes - for a couple of weeks or months there might have been labels on some machines saying “this machine does not accept the new [whatever] coin”, until the adaptations were made. It sounds like either: [ul] [li]UK vending machines makers and operators are less whiny than US ones or…[/li][li]…are less effective at whining to politicians.[/li][/ul] The US still has not accepted a dollar coin. They keep re-designing it, but every attempt fails because, every time, the vending machine industry whines about changing the size. So every new version is the same size and weight as the last, several failed versions - which is almost exactly the same size and weight as the quarter-dollar. The pound coin and the Canadian Loonie are both easily distinguishable from any other coin in your pocket. A seven-sided, thick, gold-colored, non-milled-edge extra heavy US dollar coin would be accepted. Congress needs to grow a pair. ---
**Author:** ![jjimm](https://avatars.discourse-cdn.com/v4/letter/j/ba8739/32.png) [@jjimm](https://boards.straightdope.com/u/jjimm)\ **Post date:** [January 10, 2010, 10:59am UTC](https://boards.straightdope.com/t/those-7-sided-uk-50-pence-coins/524317/28 "2010-01-10T10:59:59Z")
> [@gaffa](#): > > [ul] > [li]UK vending machines makers and operators are less whiny than US ones or…[/li][li]…are less effective at whining to politicians.[/li][/ul] Throughout the Eurozone, more than a dozen countries managed to do this in 2002 with a change to every single coin and note in the currency. It took a few months to filter through, but there was nary a peep out of the vending machine manufacturers. I presume such changes are built into the business model as an expected circumstance. In fact, most of the rest of the world manages to cope with this sort of stuff on an irregular basis. I vote for US vending machine (and cash register) companies exaggerating the difficulties, as well as more effective whining to politicians. ---
**Author:** ![SciFiSam](https://avatars.discourse-cdn.com/v4/letter/s/47e85d/32.png) [@SciFiSam](https://boards.straightdope.com/u/SciFiSam)\ **Post date:** [January 10, 2010, 11:48am UTC](https://boards.straightdope.com/t/those-7-sided-uk-50-pence-coins/524317/29 "2010-01-10T11:48:49Z")
The US dollar, in its physical from, is different to most other major currencies. The US one dollar bill has been around since 1963 and the two dollar bill since 1923. ([Apologies for the wiki link - the other sites I found were opinions or stuff for kids with no dates](http://en.wikipedia.org/wiki/United_States_one-dollar_bill). This is remarkable, especially in comparison to European and Asian currencies - the UK changes its design every ten years or so to combat fraud. Improvements in technology make it increasingly difficult to make a convincing fake UK note - it can still be done, but costs a lot more. It’s odd that the US doesn’t also change its design to combat fraud in the same way. So perhaps the resistance against a dollar coin is not due to vendors or anything small like that, but down to whatever reasons the US has for retaining the same design for the dollar bill for such a long time. ---
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [January 10, 2010, 12:09pm UTC](https://boards.straightdope.com/t/those-7-sided-uk-50-pence-coins/524317/30 "2010-01-10T12:09:31Z")
> [@Mangetout](#): > > The UK 50p and 20p coins are both curves of constant width - that is, each side is an arc centred on the opposite corner - this helps them not to jam in any chutes or channels in vending machines or other coin mechanisms. (and the coin measures the same diameter no matter which way it falls through) > > [Curve of constant width - Wikipedia](http://en.wikipedia.org/wiki/Curve_of_constant_width) (hijack, but main question’s been answered now) This used to be accompanied by the factoid that a car with 50p or 20p-shaped wheels would, surprisingly, ride smoothly. This was then debunked by the observation that these shapes have a constant diameter but not a constant radius from any point (IIRC). But now it seems to have gone “full-circle” as I see on that link a guy has made a [bicycle](http://www.china.org.cn/china/photos/2009-05/07/content_17738257.htm) with 5 and 3-sided wheels. It looks like there’s a mechanism on the front adjusting the height of the front wheel relative to the fork, but not for the back. It’s suspicious that I can’t find a movie anywhere. ---
**Author:** ![amarone](https://avatars.discourse-cdn.com/v4/letter/a/e0b2c6/32.png) [@amarone](https://boards.straightdope.com/u/amarone)\ **Post date:** [January 10, 2010, 12:10pm UTC](https://boards.straightdope.com/t/those-7-sided-uk-50-pence-coins/524317/31 "2010-01-10T12:10:18Z")
> [@scifisam2009](#): > > The US dollar, in its physical from, is different to most other major currencies. The US one dollar bill has been around since 1963 and the two dollar bill since 1923. ([Apologies for the wiki link - the other sites I found were opinions or stuff for kids with no dates](http://en.wikipedia.org/wiki/United_States_one-dollar_bill). This is remarkable, especially in comparison to European and Asian currencies - the UK changes its design every ten years or so to combat fraud. > > Improvements in technology make it increasingly difficult to make a convincing fake UK note - it can still be done, but costs a lot more. It’s odd that the US doesn’t also change its design to combat fraud in the same way. The US has made several changes to the $5 and larger bills to combat fraud. It is not worth it for the one dollar bill as it is worth so little that there is very little counterfeiting. And nobody uses $2 bills. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [January 10, 2010, 1:25pm UTC](https://boards.straightdope.com/t/those-7-sided-uk-50-pence-coins/524317/32 "2010-01-10T13:25:02Z")
> [@Mijin](#): > > (hijack, but main question’s been answered now) > > This used to be accompanied by the factoid that a car with 50p or 20p-shaped wheels would, surprisingly, ride smoothly. That was probably based on a misunderstanding - they don’t work as wheels, but _rollers_ (as in logs under a block) with that cross-section would be fine (this can be demonstrated by placing a row of the coins between two straight edges). I saw a large-scale demonstration of this on a TV programme once - I think it might have been Johnny Ball’s _Think of a number_. ---
**Author:** ![ralph124c](https://avatars.discourse-cdn.com/v4/letter/r/8797f3/32.png) [@ralph124c](https://boards.straightdope.com/u/ralph124c)\ **Post date:** [January 10, 2010, 2:03pm UTC](https://boards.straightdope.com/t/those-7-sided-uk-50-pence-coins/524317/33 "2010-01-10T14:03:07Z")
In vending machines? I kept a few of them they are so neat! ---
**Author:** ![Shakester](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/shakester/32/437_2.png) [@Shakester](https://boards.straightdope.com/u/Shakester)\ **Post date:** [January 10, 2010, 2:33pm UTC](https://boards.straightdope.com/t/those-7-sided-uk-50-pence-coins/524317/34 "2010-01-10T14:33:26Z")
Australians have been using 12-sided 50c coins since 1969. They work just fine in vending machines. ---
**Author:** ![gaffa](https://avatars.discourse-cdn.com/v4/letter/g/e68b1a/32.png) [@gaffa](https://boards.straightdope.com/u/gaffa)\ **Post date:** [January 10, 2010, 7:44pm UTC](https://boards.straightdope.com/t/those-7-sided-uk-50-pence-coins/524317/35 "2010-01-10T19:44:55Z")
> [@amarone](#): > > The US has made several changes to the $5 and larger bills to combat fraud. It is not worth it for the one dollar bill as it is worth so little that there is very little counterfeiting. They have had an issue with counterfeiters “washing” the ink off of ones to use the paper to print bogus old, pre-security measures hundred dollar bills. > [@](#): > > And nobody uses $2 bills. Actually, I have a friend - a bar owner - who buys fistful’s of them to use for tipping. His excuse is that the wait staff will remember him. Sure. As “that joker with the $2 bills!” ---
**Author:** ![zelie\_zelerton](https://avatars.discourse-cdn.com/v4/letter/z/59ef9b/32.png) [@zelie\_zelerton](https://boards.straightdope.com/u/zelie_zelerton)\ **Post date:** [January 10, 2010, 8:00pm UTC](https://boards.straightdope.com/t/those-7-sided-uk-50-pence-coins/524317/36 "2010-01-10T20:00:08Z")
I wonder if the issue with vending machines perhaps did not exist at first. When the 50p was first produced it represented a fairly decent chunk of money. Even when I was a young child (early 80s) you could buy sensible things with 50p. As in some actual groceries and not just a bar of chocolate as it is now. Perhaps it was more the case that the products found in vending machines were never going to amount to such a great price as 50p and that people were more likely to have smaller coins anyway. I remember slot machines etc at the local arcade only taking (old-style) 5p or 10p coins when I was a kid. Quite a few also took coppers. It took quite a while before prices rose sufficiently that 50p (and later 20p and £1 coins) were required. By the time that products had increased in price such that it was worthwhile changing vending machines to accept them we were so used to the coin that it wouldn’t be worthwhile for the vending machine manufacturers to complain. ---
**Author:** ![Pushkin](https://avatars.discourse-cdn.com/v4/letter/p/ee59a6/32.png) [@Pushkin](https://boards.straightdope.com/u/Pushkin)\ **Post date:** [January 10, 2010, 8:07pm UTC](https://boards.straightdope.com/t/those-7-sided-uk-50-pence-coins/524317/37 "2010-01-10T20:07:17Z")
> [@gaffa](#): > > It sounds like either: > > [ul] > [li]UK vending machines makers and operators are less whiny than US ones or…[/li][li]…are less effective at whining to politicians.[/li][/ul] Prior to decimalisation there existed a [three pence piece](http://en.wikipedia.org/wiki/Threepence_%28British_coin%29) (thruppence I think it was called for short.) It’s nicely angular, but [this PDF](http://www.brushwood.mintrasystems.com/cn4-brassthreepence.pdf) suggests it was designed with the input of vending machine manufacturers. Edited to add, zelie, if I remember my child hood correctly, it was 35p for a Twix and 45 for a tin of Lilt 🙂 ---
**Author:** ![hibernicus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hibernicus/32/2802_2.png) [@hibernicus](https://boards.straightdope.com/u/hibernicus)\ **Post date:** [January 10, 2010, 9:31pm UTC](https://boards.straightdope.com/t/those-7-sided-uk-50-pence-coins/524317/38 "2010-01-10T21:31:57Z")
> [@Pushkin](#): > > Prior to decimalisation there existed a [three pence piece](http://en.wikipedia.org/wiki/Threepence_%28British_coin%29) (thruppence I think it was called for short.) Here’s an anecdote I heard about the 12-sided thruppenny bit. It seems there was a Guinness record for how many thruppenny bits could be stacked on edge. A man submitted photographic evidence that he had beaten the previous record by 2. (e.g. if the previous record was a stack of 10, he had achieved 12). The Guinness accreditator asked for a picture of the stack of 11, and was suspicious when such a photo could not be produced. After all, the first thing you would do when you beat the record would be take a picture, before risking everything by trying to add another coin. When confronted, the man admitted that he had set up the picture by attaching carpet to the ceiling, suspending a table upside-down from the ceiling, and hanging the coins from the table using a strip of sellotape. ---
**Author:** ![gaffa](https://avatars.discourse-cdn.com/v4/letter/g/e68b1a/32.png) [@gaffa](https://boards.straightdope.com/u/gaffa)\ **Post date:** [January 10, 2010, 11:47pm UTC](https://boards.straightdope.com/t/those-7-sided-uk-50-pence-coins/524317/39 "2010-01-10T23:47:30Z")
> [@hibernicus](#): > > When confronted, the man admitted that he had set up the picture by attaching carpet to the ceiling, suspending a table upside-down from the ceiling, and hanging the coins from the table using a strip of sellotape. Way off topic, but it’s actually spelled “sellotape”? I always assumed it would be “cellotape” from cellophane. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [January 10, 2010, 11:51pm UTC](https://boards.straightdope.com/t/those-7-sided-uk-50-pence-coins/524317/40 "2010-01-10T23:51:29Z")
The brand name is Sellotape - apparently because it was distinctive enough to be trademarked at the time it was developed (whereas Cellotape may not have been) [Previous page](https://boards.straightdope.com/t/those-7-sided-uk-50-pence-coins/524317.md?page=1) [Next page](https://boards.straightdope.com/t/those-7-sided-uk-50-pence-coins/524317.md?page=3)