Instructables

Hidden compartment in a coin (with stuff you already have!)

Featured
Picture of Hidden compartment in a coin (with stuff you already have!)
One of the classic spy tools is the hollow coin where our hero (Or nemesis!) hides some microfilm, micro SD card, or a secret message. In real life, this was also used by the Soviets, when they were discovered because they were accidentally spent and dropped to reveal a hidden compartment! (Thankfully, my design does not have this flaw.)
Now, it is easy to see how cool these things are, and I decided to do some internet research. However, they seem to go for about 20.00 US dollars. I think that’s a ridiculous price to pay, especially when we can make our own with some time and money. As a result, I decided to make my own!
You can read on, or you can see the video version (The written version is more descriptive, but if you want the abridged version, check it out)

My Instructable was featured on LifeHacker! (I'm very proud...)

 
Remove these adsRemove these ads by Signing Up

Step 1: Supplies

Picture of Supplies
Seeing as this is a fake coin I was making, I choose to use the biggest commonly available US coin there is: A quarter. A nickel could also work, but then the compartment would be smaller.
So, in addition to 3 quarters, you will need…
Some info to put in it (A slip of paper, or microfilm, or even a small enough memory chip)
For tools, you will need…
-Dremel motor tool
- Drill and drill bits
- Files
- Clamps and vice (To keep our coins from getting away!)
-Solder and Soldering iron
- Hot glue/ Hot Glue gun
-Gloves (For safety!)
And a whole lot of patience. You will see why later, but believe me; it takes a lot of tries to get one of those faces just right.

Step 2: Getting the face

Picture of Getting the face
Snapshot 1 (12-14-2013 2-18 PM).png
We want our coin to be hollow. This means that we won’t need most of the coin, and so in order to make 1, we will be removing the majority of 3 coins and putting them back together like a secret agent version of Frankenstein.
To get only the face from each side, I Dremeled  down through the first face, and kept on going through the copper sheet. I stopped when I hit the face  on the other side- I didn’t want to go all the way through! I did this to 2 coins so that I had both the front and back face of a quarter.

Step 3: Getting the body

Picture of Getting the body
Snapshot 4 (12-14-2013 2-20 PM).png
Well, this is looking good and all, but I still didn’t have the main body. To solve this problem, I took a quarter and using sequentially larger drill bits, created a hole in the center. I widened and cleaned the rest up with the Dremel.

Step 4: And it all comes together!

Picture of And it all comes together!
018.JPG
So, to put it all together, I soldered one side to the ring and hot glued the other. I made sure I only used a little bit of hot glue in one spot, as the goal here isn't to keep the face on, but to allow it to act as a hinge/spring. By keeping it small, the hot glue will bend and allow the coin to open slightly, clam shell style. It will then go back into place when released. I cleaned up the solder with a file, and I was good to go!

Step 5: TaDa!

Picture of TaDa!
021.JPG
023.JPG
When it is all together, you can hide small bits of info, from a slip of paper, to microflim, or even a micro SD card. The one I have is 4 gigabytes, and that can store about 4294967296 characters. (According to the internet.) Close inspection proves it has been tampered with when it is on its own, but put it with some others or keep people from focusing on it and they will never know! (This isn't hard to do- How many people carry around only 1 quarter, and who stares at the quarter some other guy has in his wallet?) Please let me know your questions and ideas on this Instructable! Good luck in making your own, and as always, Have a nice day!
/AssemblyRequired
violeta5711 month ago
this is awesome! I can imagine exchanging secret messages with my best friend with this
theegghead2 months ago

I love secret compartments! This one is downright AWESOME!!!

hope you win the contest!

assemblyrequired (author)  theegghead2 months ago

I'm so glad you enjoyed! (I hope I win too!)

Cherrysamurai3 months ago
That's awesome!!! I hope you win! :D
assemblyrequired (author)  Cherrysamurai3 months ago
I do too :D Glad you enjoyed it!
shawno11433 months ago
sorry I thought it was but real good idea. got my vote
assemblyrequired (author)  shawno11433 months ago
Thank you!
shawno11433 months ago
this is a felony
assemblyrequired (author)  shawno11433 months ago
1) No, it isn't. The federal law makes it a felony only if it is being used for illegal acts or being passed off as a real coin.
2) Even if it was, it wouldn't matter: the federal law has bigger things to worry about than some kid drilling into 3 quarters.
3) It's my money, so as long as I treat it as it is (Not real money), then there is no problem.
4) Artists do this sort of thing all the time, as do tourist attractions (Museums, for example, sometimes have those coin presser things that will flatten a coin for a souvenir) and they don't get arrested for it.
The comments below have a very comprehensive and punctuated discussion below. Feel free to read them. In addition, I highly recommend you check out the actual law itself, which although does state that one cannot alter money, it adds the term "Fraudulently", referring to the law only being applicable when the alteration of money leads to fraud.
karalalala3 months ago
This is the best thing I have ever seen. Voted!
assemblyrequired (author)  karalalala3 months ago
Thank you, and thanks for your support! I'm glad to see you enjoyed!
mcs3203 months ago
Are you making the center thinner or are you removing the edge from the sides? I was thinking if you left a small amount on one side, and then a small tab on the inside, you could have a small watch screw to lock one side on. Harder than using glue I know, and more detailed to create, but just looking at coin compartment 2.0
assemblyrequired (author)  mcs3203 months ago
Do you mean having a tab that would be pressed by the watch screw? That would be cool, as long as I left a channel to keep the other side in line... Very clever idea!
Veda883 months ago
Did you ever buy a coffee with your secret sd card coin? ;)
assemblyrequired (author)  Veda883 months ago
Not to worry, I am proud of this one so I have held onto it! :)
IronInspired4 months ago
Very, very cool, but why would you put anything of value in a piece of MONEY??? Anyone looking to rob you/mooch off a free drink will steal this away from you! Very cool idea, but isn't there anything else you could use?          
Coin safe things like this were used by the military to give secret messages to one another. You can fit a piece of paper or, in some, a really thin San Disk USB with secret messages on it.
assemblyrequired (author)  IronInspired4 months ago
Who would want to steal 25 cents? Besides, I think the international spy agencies that used this device (KGB, etc.) would have thought of that, but they made them and used them anyway. Besides, the goal here is to be discreet, and a coin does that quite well. Yes, there is many, many other things that could be used, but I can't think of any of them that are any more James Bond-ish than a compartment in a coin-- It's a classic! In addition, the coin is the most common device of the right size that I could find. Thanks for your comment.
True, I suppose. Good idea, though!
assemblyrequired (author)  IronInspired4 months ago
Thanks, glad you enjoyed!
MajorWebUser4 months ago
Are you aware that it violates federal law to deface currency?
It depends on your intent. The statute reads:

Whoever fraudulently alters, defaces, mutilates, impairs, diminishes, falsifies, scales, or lightens any of the coins coined at the mints of the United States, or any foreign coins which are by law made current or are in actual use or circulation as money within the United States; or Whoever fraudulently possesses, passes, utters, publishes, or sells, or attempts to pass, utter, publish, or sell, or brings into the United States, any such coin, knowing the same to be altered, defaced, mutilated, impaired, diminished, falsified, scaled, or lightened - Shall be fined under this title or imprisoned not more than five years, or both. [Emphasis added.]

This is why penny pressing machines are legal.
They are currently trying to pass a law that makes it illeagle to melt down penny to collect the copper... the penny has more copper value in it than it does monitary worth.. Even the new(ish) penny's that are only plated with copper are worth more than the face value...
But it's not illegal *yet*, and that's all that matters.
Are you aware that it's illegal to sing happy birthday in public without paying royalties to Warner Chappell?
Not true. I just finished watching a program on the National Geographic's Channel on the US Mint. The director of the mint was asked about what a person can do to money they have. He stated: "You can do whatever you want to with a coin or bill. It's your money, you own it." He further commented that as long as you didn't attempt to defraud someone like perhaps attempting to turn a $5 bill into a $50 bill, anything you want to do is legal.
assemblyrequired (author)  MajorWebUser4 months ago
Yes, but only if I use it for illegal things (Counterfitting, etc.) Also, the Secret Service has more important things to worry about than some kid messing with quarters.
All of your ibles have one problem... They are too awesome!
Absolutely terrible, isn't it :)
Yeah, it's a real problem
assemblyrequired (author)  nbnoahbezzant24 months ago
Too bad I may never be able to fix this problem... :D
Glad to see you enjoy them!
presto024 months ago
thanks, that suff is nice to know.
assemblyrequired (author)  presto024 months ago
Yup! :D
kjlpdx4 months ago
a router could do this cutting quite clean and easily.
assemblyrequired (author)  kjlpdx4 months ago
If only I had one! One of my goals is to create Instructables that people with a basic tool kit could pull off, and so I wouldn't have made one forcing people to use tools they might not have, preventing them from trying this. However, a router would make this easier if you could get one small enough for a coin. he closest thing to that is a Dremel, and you may remember that that is what I used.
mcrawford24 months ago
Actually, it is no longer illegal to deface u.s. money
dflamm mcrawford24 months ago
Actually, it is illegal. Based on this information. It is legal to deface PAPER money, but not COINS! As for the comments that it's "only 75 cents". Go ahead, piss the Feds off. People get legal action taken against them for all kinds of stuff. I'm just sharing the info. Have fun.
http://voices.yahoo.com/is-illegal-write-draw-us-5839668.html
Um, wrong. It is NOT illegal to alter or deface ANY form of money, paper or coin. It is only illegal to modify money with the intent to defraud another, such as by modifying its denomination.
Even more to the point, your link has NO authoritative information at all. And more onerous, contains links to a phishing site. Nice.
Yes, I remember in San Francisco a small machine in the street that can trasform your coins in to a nice souvenir of the town - funny
assemblyrequired (author)  mcrawford24 months ago
Good to know!
Pro

Get More Out of Instructables

Already have an Account?

close

PDF Downloads
As a Pro member, you will gain access to download any Instructable in the PDF format. You also have the ability to customize your PDF download.

Upgrade to Pro today!