Can anyone explain how this occurred?

[cpm9ball]

In the course of packing some odds & ends for my impending move, I "rediscovered" 6 - 2001P Kennedy's that I had set aside back in 2004. I found these interesting because they all have ripples on the obverse. These ripples appear to look like they could be shockwaves as you might see emanating from the epicenter of a blast. Ordinarily, I am accustomed to seeing the planchet metal flowing toward the rim looking somewhat like a starburst (for lack of a better description). As a matter of fact, you can still see this metal flow surrounding the ripples.

 

In no way do I consider these error coins, but I just want to try to understand how this could happen during the coining process. Is it possible that the planchets were overheated before striking which brought the metal closer to a liquid state? That is the only conclusion I can draw from this. Does anyone know or have an alternative explanation for this?

 

Thanks!

 

Chris

[physics-fan3.14]

That is kind of a cool effect. Just to be clear - the mint does not heat the planchets before striking. Coins are struck at room temperature, but the friction of striking does heat the coins.

 

Could this possibly be a die fatigue effect? Similar to orange peeling? I'm not sure, just throwing out the possibility.

[coinman1794]

It could be a die defect, a fatigued die, or a defect in the planchets that shows after striking (but this looks like it's from the dies, to me).

[TomB]

I've found a few of these, too.

[Oldtrader3]

My engineering guess is that they look like cutting tool marks on the die surface from a lathe that were not polished out?

[gmarguli]

It's the result of a worn die. I submitted a couple of state quarters to ANACS with this effect and that's what they called them.

[jackson64]

it does look like striations made during the planchett manufacturing--but I'm guessing that the actual striking of the coin should/would have "flowed" those lines away...you got me..

[DWLange]

I'm with Oldtrader. Those look like lathe lines that should have been polished off the die stock before it was hubbed to produce the finished die.

[Conder101]

Yep lathe lines either not polished off the die blanks before hubbing (I have some high grade Conders, especially those with mostly text that show the lathe marks over the entire surface.) or in some cases they can be caused by the cutting tool from the reduction of the model. But usually those lines are in protected areas of the field. You will often see them behind the cross and through the leaves and at the bottom of the white stripes on shield nickels. They also often show up through the stars and rays or just the stars on the reverse of the shield nickel. They were having to make so many dies that they didn't have time to finish or polish them properly. (Lines on the devices could be polished off the hub, but those in the protected field areas had to be polished off the dies.)

[cpm9ball]

Thanks alot, guys! OT3, your explanation sounds a lot more plausible.

 

Chris