How to determine if your coin has been struck on wrong thickness stock.
Let’s do an experiment together. Let’s try to figure out this coin.
Imagine you have a clad quarter in your hand, but this coin seems awful thin for a quarter. You pull out another clad quarter and compare. The suspect quarter sure looks thinner. The design on the suspect quarter obverse and reverse of the coin look OK, the coin is just THIN.
How can you prove what this clad quarter is on? There IS a way to find out if it is struck on wrong thickness stock.
- First we will need to do a little bit of technical stuff. Find a known good scale and weigh the coin.
- For our experiment, we will use the weight of 4.16 grams.
- We look at the coins edge or reeding and we see some copper there, so that might help.
- Now in order to work the formula for this struck on wrong thickness stock, we need to get coin specifications. No better place to get specifications on coins, than the US Mint itself:
Now, looking at the US Mint Coin Specifications chart and what we know about this clad quarter that is thinner than normal, we have to make a choice. We know it is silver in color, so that eliminates the Lincoln cent and Sacagawea/Presidential dollars too. So now our possible struck on wrong thickness stock candidates are the Nickel, Dime and Half-Dollar.
What do you mean struck on wrong thickness Stock ?
Struck on wrong thickness stock is exactly as it says. Some one at the US mint took a sheet of prepared metal and fed it into the machine that punched out quarter planchets (coin blanks). They probably expected that pile to be all of the same type metal and thickness, so they are just doing their job. The metal was thinner than normal and it was sent into the machine and it cuts out correct quarter size planchets and then these are set down the assembly line to make coins.
So with struck on wrong thickness stock, you get the correct size of coin but the THICKNESS of the coin is off.
Struck on wrong thickness stock is not Struck on wrong planchets
So now you know what a struck on wrong thickness stock is. I want to ensure you do not confuse this with struck on wrong planchet, because they are totally different. The best way to identify if a coin is struck on a wrong planchet is to weigh that planchet. The weight of that coin should match up very closely to the US Mint specifications chart.
Back to the struck on wrong thickness stock project !
Let’s say we take a Nickel, a Dime and a Kennedy Half Dollar and lay it along side the struck on wrong thickness stock candidate. Our general impression should be that one of those coins, the Nickel, Quarter or Half should be close to the same thickness of the struck on wrong thickness stock. Once we compare them all, it looks like the Dime MIGHT be the best bet.
But, how do we prove this coin is Struck on wrong thickness stock?
Sharpen up your pencils and grab a calculator, it’s about ready to get scientific. A good amount of math – easily explained is headed your way.
So we have some data, but we need to hit the jackpot and solve for the correct weight of 4.16 grams or within +/- 0.2 grams. Anything over +/- 0.2 grams very well mean the candidate is probably just on a thick or thin planchet.
Since the Dime was the closest in thickness, let us start with that coin. From the US Mint specification chart we need some info that is shown within the chart below.
We use the normal clad dime weight (2.27 grams) the known diameter of the dime (17.91mm), plus we know the Quarter diameter as well (24.26mm). For an area, you need the radius, which is one-half of the diameter. PI is used to determine area. The rest is easy.
Here is the formula for the struck on wrong thickness stock candidate we are looking at:
Six easy math steps to determine if a coin is struck on wrong thickness stock
Cool ! It’s a match on the first try ! That was pretty easy. The hardest part of this experiment was behind the scenes. I had to take an already provided struck on wrong thickness stock formula and try to figure out what it was saying. In the end, this example is much more comprehensive. I hope you learned something.
This formula can be used on just about any coin combinations, all you need to do is plug in three of the four variables at the start and you are on your way.
Not a big fan of struck on wrong thickness stock error coins? Take a look at our major mint error coins called Die Caps: Die Cap Major Mint Error Coins (minterrors.org)
Looking for “normal” coins? Please see Shop – US Coins, Silver Bullion and Numismatic products and services – TheCoinStore.org
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