Clearing The Air: MD Vs. DD - Coin Community Forum

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Author	Replies: 4 / Views: 1,749
BlueSolo Pillar of the Community United States 740 Posts	Posted 03/21/2015 7:59 pm Maybe this is obvious to most people, but I would like make this post to clear up some confusion between MD and DD. Please let me know if my observations are valid. While this may only work for coins in nice condition (worn coins may remove this effect), one of the things I have observed when examining coins for Double Dies is this striation which helps me determine it is Machine Doubling. I figured this is from the coin shifting during the strike. The shift causes the die to scrape the top of the second image on the MD coin which is evidenced by all these red lines in the image below. I also figure that the coin shifts during the strike in the direction of the orange arrows. Here are a few more examples: The reason this striation would not appear on a true DD is the doubled image is on the die itself. The coin does not scrape in a DD because the image is imprinted onto the coin as if it was by design. As we see with imprints that are by design, this scraping does not occur. I have also been reading about MD causing a reduction of devices. Does this mean, as an example, a font in 12 font has an offset and appears to be 11 font while DD stays 12 font in both appearances of the image? Edited by BlueSolo 03/21/2015 8:10 pm Report this Post to the Staff

coop Bedrock of the Community United States 62064 Posts	Posted 03/21/2015 8:12 pm I agree with most you have stated. Just one minor point. Quote: I also figure that the coin shifts during the strike The coin is held in place by the collar thus making the coin round and not moving. It is the dies that are shifting and moving during the strike. The striation lines are from the metal on the die. If you take a sharp knife and slide (not to cut into the cheese, dragging the sharp edge) it across a piece of cheese, you can see the same affect. You will see the highs and lows that the metal edge creates on the cheese. The edge of the devices that show wear, creates the same striations you are seeing on your coin. Quote: 12 font has an offset and appears to be 11 font while DD stays 12 font in both appearances of the image? The doubled die font size could be 14-18 (depending on the spread of the hubbing) because the die is doubled. It would be much larger than a 12. Other wise it would be a normal die. But you still are headed the correct direction with your thinking. Report this Post to the Staff
SsuperDdave Moderator United States 23522 Posts	Posted 03/21/2015 8:14 pm Well, to start with it's the die that moves during Machine Doubling, not the coin. The coin is enclosed by a collar so tightly the collar impresses the reeding onto the coin. Coin isn't moving. The striations are from metal being forced to flow like a liquid. That's why you see it in the fields. The "reduction" part is because Machine Doubling usually reduces the actual size of the device by the thickness of a doubling. A machine-doubled 9 and a normally-struck 9 are the same outside size. Report this Post to the Staff
BlueSolo Pillar of the Community United States 740 Posts	Posted 03/21/2015 8:19 pm Great! Thanks Coop, I've been having a lot of trouble with the distinction but now I feel more prepared. I read the coin or the die could be moved during the strike but the collar explanation eliminates the coin moving. Could the coin rotate in the collar though and have a similar effect to the die shifting? Edit: SsuperDdave: Guess the coin being held so tight eliminates the coin rotating : ) Thanks Edited by BlueSolo 03/21/2015 8:20 pm Report this Post to the Staff
SsuperDdave Moderator United States 23522 Posts	Posted 03/21/2015 9:14 pm The dies aren't held nearly as tightly as the collar. Heck, the collar flat stops metal flowing like water under 150 tons of pressure. The dies, though, can be held responsible for all sorts of differing error coins because they flopped around. Report this Post to the Staff
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