I saw a hollowed out US half dollar in this reddit post, and thought "I wish all my coins were like that".


Doing a quick search around, most coinage seems to be quite solid. There seem to be some around, like a few of the Japanese yen coins with a hole right in the middle, but none to quite this degree.

I'm far from an expert on these things, but it would seem that making mostly-hollow coins would greatly decrease the amount of material required, as well as lightening the physical weight a lot of people's pockets.

Why aren't there more hollow coins around?

  • 6
    I'm voting to close this question as off-topic because it relates to physical, rather than financial, aspects of coinage. May be better at engineering.stackexchange.com.
    – nanoman
    Apr 2, 2019 at 10:38
  • On top of the answers below, let's not forget that many people keep coins in their pockets. How many times would you have to unravel junk from the inner details before you gave up carrying coins entirely? Plus, what about vending machines and the string coin trick? What happens when the center piece falls out due to bad design or anyone messing with it enough. What's the policy on bringing fragments to a bank? The idea of hollowing out coins is limited to just neat shops at places like the renaissance fair. That's about it.
    – Kai Qing
    Apr 2, 2019 at 17:09
  • @KaiQing Coins already do have holes in them (Japanese Yen), and coins do have center pieces that fall out (Canadian Toonie), so those problems have been dealt with.
    – user71659
    Apr 2, 2019 at 18:58
  • @user71659 - not like the picture in the post. I saw those recently at a fair and while they are pretty cool looking they would be problematic for actual currency. A hole in the middle wouldn't snag like pretty much any of the details in a cut coin
    – Kai Qing
    Apr 2, 2019 at 20:28
  • @nanoman OK. I posted here because it really wasn't obvious to me where this question should go, and I saw a few other questions about physical currency. Never would have occurred to me in a million years to post on engineering. Would be grateful if a mod moved it to an appropriate place, rather than closing. Apr 2, 2019 at 21:24

2 Answers 2


In addition to the manufacturing problems, unless you do something like an internally-braced honeycomb structure (which REALLY increases your manufacturing costs :-)), your hollow coins will be weak and easily crushed, like a tin can.

Another problem is psychological: many people still think coins have intrinsic worth, because of the metal. Lighten the coin, and people think it's worth less.

  • Not sure what an internally-braced honeycomb would be/look like, but what about filling it out with some unobtrusive lightweight material, like a sturdy but clear plastic? (At which point it's not hollow anymore, but would probably still look cool) Not sure why it would be important for people to think the coins have intrinsic worth. Apr 2, 2019 at 21:30
  • I see the OP has added a picture, and that's NOT what I understood by "hollow". To me, that means a solid surface and empty interior, like a can. (Not sure what you would call that carved-out coin.) WRT weight=value, the psychology basically devalues the whole currency. If lightweight coins were desirable, they could be minted from aluminum, but the countries that do tend not to be major international currencies.
    – jamesqf
    Apr 3, 2019 at 16:20

I'm far from an expert on these things, but it would seem that making mostly-hollow coins would greatly decrease the amount of material required,

But it would radically increase the manufacturing process. Right now coins are made much the same as a wax seal, some bit of metal is struck with a die. Sure, you could strike through the metal like a cookie cutter but that would leave sharp unfinished edges, here you have added manufacturing process and not saved any metal.

The coin in that image is nowhere near as durable as it was before being cut up. There are a lot of reasons not to do that with money.

  • Can you elaborate a bit on your answer? Why would the cookie cutter not save any metal? And what are some of the "reasons not to do that with money"? (Some of this might seem blindingly stupid/obvious, but I swear I'm asking in good faith) Apr 2, 2019 at 21:40
  • it would save metal insofar as the scraps could probably be sent off to a recycling center to recoup some of the cost but the input material would the same unless there was a shift to some sort of injection process which would require radically more expensive tooling. I'm sure there's a video on the internet of a coin production center, the process is extremely simple. If you were to introduce a lot of edges you'd introduce a lot of surfaces that need finishing which would bring a lot of time and increased costs.
    – quid
    Apr 2, 2019 at 21:45

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