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Thread: AGE Weight, Ping and Shimmer details

  1. #1

    Default AGE Weight, Ping and Shimmer details

    Thought I'd post some precision measurements I made on a few AGEs dated 1993, 2004, and 2008. Here are the details of the three coins. The coin and weight is in the first line. Then the two fundamental ping frequencies followed by the two harmonic ping frequencies. Also the shimmer frequency is listed as "dif=...."

    As an aside, measurements on a tube of 2009 AGEs straight from a sealed monster box produced shimmer frequencies that ranged from 8Hz to 34 Hz. So don't expect the "shimmer" beat sound of a coin to indicate real v counterfeit.

    Most notice when pinging that sometimes one gets a noticeable "shimmer." This is because there are actually two close frequencies that happen when you ping coins. The energy imparted to the coin quickly separates into two distinct frequencies. These are the resonance frequencies for the slowest path and fastest path for the edges to vibrate but not the center which is fixed. The difference between these two frequencies is what creates the "shimmer" and it can vary quite a lot between coins. Even from the same year and tube. Also, how much shimmer one gets depends on where on the edge the coin is tapped. The amount of shimmer can vary from none (just a decaying tone) to distinct. However, the frequency of the shimmer is always the same for any specific coin as are the two tones from the base resonance and harmonic.

    AGE 1993, 33.9460g
    Fundamental
    4593.99
    4624.39 dif=30.40
    Harmonic
    10564.87
    10571.13 dif=6.26

    AGE 2004, 33.9611g
    Fundamental
    4534.77
    4568.70 dif=33.93
    Harmonic
    10401.38
    10405.81 dif=4.43

    AGE 2008, 33.9877g
    Fundamental
    4540.59
    4563.73 dif=23.14
    Harmonic
    10542.98
    10546.39 dif=3.41

  2. #2

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    that's taking PM fondling to a whole new level

  3. #3

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    Quote Originally Posted by yellowsnow View Post
    that's taking PM fondling to a whole new level
    Yeah And I am a techie nerd. Not just a stacker.

    Actually, it comes from investigating creating a set of metrics to identify a coin, or coins, from a set. For example, a way to verify that the coins you send to someone are the same as the ones should they return them. Think of it as a way to fingerprint the coins in your stash.

    Aside from weight, which requires an analytic scale and those aren't cheap, there are 4 metrics that are relatively uncorrelated with each other. They are:

    1. the differences between the tones. Both fundamental and harmonic.
    2. the ratio of the mean fundamental and harmonic tones.
    3. the mean fundamental tone.

    These can all be measured with a smart phone or other cheap audio capture devices. I have a set of 6 Olympus recorders and all have accuracy of less than 5 ppm out of the box.

    Item #3 suffers from being very sensitive to temperature changes. A 1 degree C change shifts the frequencies about .03% . So being able to measure it to .01 Hz is not very useful absent insanely controlled temperature.

    Items #1 and #2 show minimal correlation with each other and are not nearly as temperature sensitive. A side benefit is that the audio sampling doesn't have to be as accurate. I calibrated my audio sampling equipment using WWV over several hours which produced accuracy of better than 2 PPM.

    So I'm kicking around the idea of making an app for smart phones. I have the code in c++ and Matlab for analyzing the pings and just need to add database stuff and a visual interface to make a smart phone app.

  4. #4

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    Quote Originally Posted by redmonster View Post
    Yeah And I am a techie nerd. Not just a stacker.

    Actually, it comes from investigating creating a set of metrics to identify a coin, or coins, from a set. For example, a way to verify that the coins you send to someone are the same as the ones should they return them. Think of it as a way to fingerprint the coins in your stash.

    Aside from weight, which requires an analytic scale and those aren't cheap, there are 4 metrics that are relatively uncorrelated with each other. They are:

    1. the differences between the tones. Both fundamental and harmonic.
    2. the ratio of the mean fundamental and harmonic tones.
    3. the mean fundamental tone.

    These can all be measured with a smart phone or other cheap audio capture devices. I have a set of 6 Olympus recorders and all have accuracy of less than 5 ppm out of the box.

    Item #3 suffers from being very sensitive to temperature changes. A 1 degree C change shifts the frequencies about .03% . So being able to measure it to .01 Hz is not very useful absent insanely controlled temperature.

    Items #1 and #2 show minimal correlation with each other and are not nearly as temperature sensitive. A side benefit is that the audio sampling doesn't have to be as accurate. I calibrated my audio sampling equipment using WWV over several hours which produced accuracy of better than 2 PPM.

    So I'm kicking around the idea of making an app for smart phones. I have the code in c++ and Matlab for analyzing the pings and just need to add database stuff and a visual interface to make a smart phone app.
    best is to check what's available app already
    https://www.youtube.com/shorts/15K4TlJpcGc

    best is to have a datbase of tone profile for each type of coin.

  5. #5

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    Quote Originally Posted by yellowsnow View Post
    best is to check what's available app already
    https://www.youtube.com/shorts/15K4TlJpcGc

    best is to have a datbase of tone profile for each type of coin.
    There are good apps already for associating ping freqs with coin types such as AGEs, ASEs, Maples, etc.

    What's needed is a way to ID each coin by measuring a set of attributes. For example, just looking at a single attribute, the difference in the two fundamental freq. tones on an AGE allows one to exclude 95% of other AGEs. Looking at the difference in the harmonic freqs. excludes another 90%. And using the ratio of the fundamental to harmonic would exclude another 90%. Now we are at the point that a random AGE from the same monster box has a 99.95% chance of being detected as not the same coin.

    And that's before comparing weight or the fundamental freq. itself. The latter is a bit more expensive and time consuming but doable where it's important to know.

    The point would be to have a way to track coin returns to make sure they were not swapped out or to track stolen coins to verify they weren't popping up and getting sold to local coin stores.

  6. #6

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    The problem with that is that even handling and a little finger oil on a coin will give a different reading, if your app is sensitive enough to differentiate between same types of coins. Even temp difference will give a different sound.

  7. #7

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    Quote Originally Posted by shades View Post
    The problem with that is that even handling and a little finger oil on a coin will give a different reading, if your app is sensitive enough to differentiate between same types of coins. Even temp difference will give a different sound.
    Yes, as I pointed out, temperature has a very big effect on the fundamental and harmonic freqs. So you would need a freq difference of 3 Hz or so to exclude a match.

    But that sensitivity is reduced a few orders of magnitude when looking at the freq differences. And I've tested that. So the 3 main metrics, the Hz diffs of the base and harmonic pairs and the ratio of their middle freqs, are not very sensitive to temp.

    As for handling finger oils and even scuffs and small scratches. These have, perhaps surprisingly, little effect. Even on the high precision Hz readings. Haven't scratched AGEs but have with some ASEs and the effect is not measurable. Even for weight, you have to leave very visible grease to get a change in the sub milligram level.

  8. #8

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    In the past, I used spectrum analyzers and built a library of known resonance frequencies for coins that I wished to trade. Then a good quality phone app came my way & I started using that instead.

    The phone app is limited in the number of coins that it recognizes, but it is convenient to use, so I restricted my future purchases to just the coins that were known to the app.

    I was surprised that the same app I was using on android was not available for an I phone. I phone apps seem to be hard to come by.

    The resonance test can be fooled by certain alloys, but those alloys don't pass the weight/density tests nor the electronic tests, like a PM verifier, or even the cheaper ones.

    There is also an alloy that will fool the electronic testers, but it does not pass the other tests.

    I don't completely trust an audio harmonic (ping) test alone, but it is a darn good place to start as it's both inexpensive & non-destructive. It can weed out a lot of the classic fakes pretty quickly. Tungsten cores don't stand a chance against a ping test.
    Last edited by SilverPalm; 10-17-2023 at 04:45 AM.
    “The Federal Reserve is not currently forecasting a recession.”
    Fed Chairman Ben Bernanke, January 2008
    This is no longer posted in the Fed Minutes of January 2008, but still quoted here - https://www.nbcnews.com/id/wbna22592939. The FOMC minutes still quote MR. Reifschneider. as stating the same thing.

  9. #9

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    Here's high precision weight and frequencies from a tube of 2009 AGEs

    Weight(g) - tone1 - tone2 - tone3 - tone4
    33.9665 4485.81 4499.24 10466.99 10470.95
    33.9491 4490.74 4506.55 10475.70 10480.38
    33.9845 4486.71 4514.09 10487.57 10491.00
    33.9749 4486.10 4501.79 10476.33 10479.03
    33.9771 4486.96 4514.72 10483.65 10488.29
    33.9860 4495.29 4516.89 10487.91 10491.75
    33.9463 4483.30 4506.40 10473.00 10474.24
    33.9594 4481.59 4509.99 10475.42 10479.84
    33.9535 4488.08 4514.99 10484.56 10488.01
    33.9724 4484.60 4513.08 10480.60 10484.51
    33.9831 4485.57 4519.72 10489.15 10493.10
    33.9580 4479.01 4506.14 10472.12 10475.65
    33.9557 4481.62 4509.13 10475.47 10479.23
    33.9748 4486.79 4502.42 10479.82 10483.21
    33.9595 4481.61 4514.19 10478.28 10481.91
    33.9573 4486.04 4505.42 10469.91 10474.31
    33.9639 4482.56 4510.43 10477.97 10480.76
    33.9695 4483.04 4502.33 10468.06 10470.77
    33.9773 4487.66 4501.68 10474.86 10478.82
    33.9858 4493.68 4501.60 10477.18 10481.83

    Frequencies were measured at an ambient temp of 22C. All frequencies shift by -.018%/DegC. This affects resonant frequencies more than freq differences. For instance a 1 degC increase in temp will decrease the low freqs by .81 Hz. But will only change a 7.92 Hz dif by .001 Hz so the upper and lower differences retain their ability to distinguish between coins even when temperature or sampling precision is not well controlled.

    This level of precision is not needed for verification of AGEs but rather it possible to "fingerprint" one or more AGEs using a smart phone app with a high precision spectrum capability and, optionally, a precision scale for weight.

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