Search for fake coin in Topics


Counterfeit or Error coin? Answered

Hello, I have a 50 pence coin that I noticed because it was not accepted in a vending machine. On comparison with another coin of the same year it became obvious that something was awry. I don't mind because I like fake coins, they are interesting. It is noticeably thinner and at least a gram lighter; it just feels less substantial. The rim on the upper half of the coin on both sides has either worn away or was never there. I looked on the Googles but can only find information on counterfeit pound coins, of which there are millions ( between 1:50 and 1:200). It seems that a 50 pence may be too low in value to fake. Are there any coin collectors out there who know whether this is likely to be a fake coin or an error coin. If it is an error coin does it have a value. Thank you. PS Through reading around, I discovered that the 50 pence is a special shape; despite its  odd shape it has a constant diameter.

Question by FriendOfHumanity    |  last reply


Fake devices

I just took apart a cheap "solar" calculator that was actually powered by a small coin cell. The "Solar Panel" was colored cellophane. You ever find something like this?

Topic by Rotten194    |  last reply


The sound of a bad penny - Finding counterfeit coins by sound

Acoustic method could quickly catch counterfeit coins.You might assume that counterfeiters only bother with high-value bank notes, but there is a chance that some of the coins jangling around in your pocket right now are fake. If Mototsugu Suzuki gets his way, it may be that jangling that gives them away.Suzuki, a researcher at the Tokyo Metropolitan Police Department's Criminal Investigation Laboratory in Japan, has developed a way of examining coins based on the sound they make.In Suzuki's method, coins slide down a slope and then fall onto a brass block. The sound they make on impact is relayed via a microphone to a computer.Although the human ear cannot usually tell the difference between real and fake, a computer can. Genuine 500-yen coins showed four distinctive peaks of natural resonance frequencies in the 5-20 kilohertz range. This was not the case for fakes; some fakes produced only three peaks, while others showed four but at different frequencies to genuine coins.In addition to helping detect counterfeits, the sound data could be used to build up a database of fake coins, suggests Suzuki. This might help law enforcement officers to prove how many coins one counterfeit operation is responsible for. This would make for an awesome Instructable! Start with these two Instructables and get dropping pennies! https://www.instructables.com/id/Build-a-dsPIC-Oscilloscope-and-Spectrum-Analyzer-/https://www.instructables.com/id/Low-speed-AVR-oscilloscope/

Topic by ewilhelm    |  last reply


How do I determine if something is lead?

I found a hideously fake £2 coin in my change, I bit into it to double check and it left a noticeable tooth mark (also upon closer inspection the gold bits were rubbing off and it had an overall wedge shape to it). Because it's nice and soft and now worthless as currency, I thought I'd try that turn a quarter into a ring instructable with it. After only a few taps I saw a noticeable difference and it now occurs to me that it's probably made of lead. Bottom Line: - Dulled silvery metal - Very soft (can leave toothmarks if I bite hard) - Need a definite way to tell if it's lead before I attempt to make a ring out of it. I know it's not gonna kill me unless I keep attempting to take bites out of it, but I'd still like to know, thanks. (also I don't have access to any chemistry equipment for proper tests)

Question by madmanmoe64    |  last reply


The Instructables Rating System

As you have all noticed, Instructables has recently implemented a new rating system, based on stars (insert 2001 A Space Odyssey joke here). We've done a bit of experimenting -- and reserve the right to do more in future -- but it's stable for now so here's how it works. UPDATE 2010-09-24: The below calculation has been tweaked to bring Instructables' ratings closer to the level of ratings of comparable content on the Internet generally.  We found that we run about a star low, based on a rough look at a bunch of other sites and our (totally unbiased of course!) estimates of their content quality.  So, we have added a star to all ratings across the board.  It's like grade inflation... but we know our users put up really good stuff and we want that to be recognized. UPDATE: we've tweaked the system a bit more. The below describes the rating system as of 2008-11-15. The rating system uses a weighted average, where Instructables with only a few ratings, or ratings by users who have not rated many Instructables, have a total closer to the middle of the star range than the actual average of the ratings. For example, an Instructable with one five-star rating will have a total closer to 4 than to 5, because there are so few ratings on it. If the user who rated it hasn't rated other Instructables, the total will be lower than if the user who rated it has done a lot of rating in the past. The purpose of this difference is to minimize the effect of 'shill' ratings; we've seen some members attempt to bump their ratings by creating fake accounts just to rate up an Instructable or two! As more people rate each Instructable, the total becomes closer and closer to the true average of the ratings. And as each user rates more and more Instructables, we weight their rating higher and higher. We have done it this way because we want the rating to reflect the opinion of the whole community, and we believe that members who do a lot of rating have been around enough to have a good sense of what makes a good Instructable. Also, members who comment and rate have their rating counted higher, as the comment indicates a higher level of involvement with the Instructable than rating alone. This method makes it so a less-than-stellar Instructable can't be pushed to the very top of the ratings because the author got their friends to sign up and rate it at 5 stars; similarly a really good Instructable can't be dragged too far down by a malicious user. For the mathy amongst you, this is the formula (we changed the way one component is calculated): (siteAvgNumRates * siteAvgRating) + (numRates(ible) * avgRating(ible)) R(ible) = ---------------------------------------------------------------------- siteAvgNumRates + numRates(ible) The avgRating(ible) is no longer a straight average, but a weighted one. It's calculated like this: (W1*R1 + W2*R2 + ... + Wx*Rx) + 2(V1*C1 +V2* C2 + ... + Vy*Cy) -------------------------------------------------------------- (W1 + W2 + ... + Wx) + 2(V1 + V2 + ... + Vy) Pretty complicated algebra, huh? W and V are both weight values, between 0 and 1. R is the rating of someone who has not commented, and C is the rating of someone who has commented. siteAvgNumRates and siteAvgRating are estimates, held constant in the pursuit of not having ALL ratings change every time one person rates one Instructable. As you can see, when the number of ratings for a particular Instructable is low, the weight of the site averages count for much more of the rating value. When the rating count is high, the site averages are only a small part of the total rating value. We believe this algorithm has a good balance between letting the cream rise to the top, and preventing 'rating spam' to coin a term. Please comment!

Topic by rachel    |  last reply