Featured Large Cent struck on Defective Planchet

What tells are you seeing?

The “bend” is from whatever caused the damage on the reverse. It is cup-shaped, meaning the damage resulted from pressure or an impact. I’ve seen coins hit by bullets which have not broken like this coin has.

What do you mean by these?

Which strongly suggests that the fracture is due to a localized flaw.

I have a 400x digital microscope that can be used to magnify any point of the break if that helps.

 

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1: There is another secondary crack on the obverse which hasn't yet fully propagated to the reverse.
2: Surface texture and changes in surface roughness. Generally speaking, the roughness increases as a crack propagates, so the fracture progresses from smooth to rough. In some cases, the initiation side can be determined by the straightness of the fracture edge. It appears the fracture is smoothest at the center on the observe side and then becomes rougher as it propagates towards the reverse and edges of the coin. Correct me if I'm wrong on this.

Yes, the impact on the reverse side creates tension stresses on the obverse side. If you bend something until it breaks, what side does it break from? And no, it was not hit by a bullet.

There are four types of fracture mechanism in metals:
1. Ductile
2. Brittle transgranular
3. Brittle intergranular
4. Fatigue

Beach marks and ratchet marks are both fatigue features. It it best to view fractures using "glancing light". Try turning off the overhead light, take a flashlight and shine it across the fracture surface from the side. This will creates shadows that will better highlight the surface topography.

It just rules out inherent brittleness (e.g. faulty heat treating). Macroscopic brittle fracture can occur in a ductile material for other reasons such as rapid loading (high strain rate). Take some taffy or slime and try pulling it apart very rapidly versus very slowly. Pulling it slowly will cause it to stretch and deform a lot more before breaking. Pull it apart fast and it will immediately break with little deformation. Same is true for ductile metals.

Lets see a higher magnification shot from the fracture origin. Near the center on both obverse and reverse edges, in case I was wrong about which side it initiated from.

 

Hope you don't mind entertaining a slightly different theory.

https://www.coinworld.com/news/us-c...emble-other-forms-of-brittle-failure.all.html

The more I look at this, the more I think it was a cracked planchet error. The crack occurred prior to or during striking, but it did not fully propagate across the coin so the two pieces were still held together by some ligament. The crack is brittle due to possibly missing the annealing treatment, alloy impurities/defects, and the high constraint between the collar and dies (there was no room for it to deform).

The damage on the reverse was a separate event that happened at a later time and may have been what finally broke the ligament apart. This strike shows more ductility because the coin was no longer constrained between the collar/dies so it had room to bend and deform. Someone may have tried to crimp or cold weld the pieces back together (there is some smearing of the fracture surfaces).

I do not believe it cracked after striking because there had to be some applied stress to cause it to crack. The strike on the reverse would not cause a crack so far away from where it was hit (the stresses decrease further away from the strike) which is why I believe these were two separate events. If the coin was used in some way where it experienced tensile, bending, or compressive stresses, then I would expect to see more marks or damage on the surfaces apart from just the crack. The fracture surface also shows heavy oxidation which indicates it is an older fracture that has been exposed to the environment for a while.

Getting into the specific fracture mechanisms, crack propagation path, loading conditions, etc. is going a little too deep into things and isn't really necessary to determine it is most likely a defective planchet.

 

There are some points along the break which do not have the “crumbly” texture. There is evidence that these were bent and snapped apart. These are the ligaments you are talking about, but they make up very little of the fracture surface.

Have you ever hit something hard that had a major flaw, and the resulting resonance caused the flaw to exacerbate and fail completely? That’s what I believe happened here. I already postulated that the flaw was already there before the event causing it to fracture.

Sorry, pictures are coming eventually. Things have been busy.

 

Sorry for the delay.

These are along the edge of the break of the larger piece. The top edge is the obverse.



This is along the break seen from the reverse side of the larger piece.



Here is the "crack" on the obverse. As you can see, it is very shallow and looks more like a planchet flaw (lamination) than something post-mint



Along the break on the obverse side of the larger piece.

 

Along the edge of the break on the reverse of the small piece.



Matching the two halves on the reverse, noting in particular the compressive damage along the break.



Here is a closeup of a still-intact flap of metal which originally bridged the two pieces.

 

And, finally, matching the two halves along the obverse.



There is an imprint of another coin here (10:30). There is a similar impression at 4:00.



All in all, I am not seeing damage consistent with being bent to the point of breaking. It really looks like a planchet flaw that split post-strike.

 

@GDJMSP @desertgem @physics-fan3.14 care to opine?

 

It appears that there may be larger grains in the copper which could be an indication of an improper alloy, contamination, or an annealing issue. These could be localized to the fracture region or be throughout the planchet (I believe they are in the entire planchet, but no proof to support that).

Please note, I am not a metallurgist nor am I familiar with a typical microstructure of this type of copper, but believe the large grains are an anomaly. I welcome additional comments or corrections from members with more experience in metallurgy.

 

A properly produced planchet (or any other adequate working metal) has satisfactory homogeneous metal properties. This coin planchet apparently was non homogeneous, resulting in a weakened zone in the area of the crack. If the weakened metal is over stressed, due to a applied force, a strain (in this case a crack) results.

The above opinion is based upon my Structural Engineering background in strength of materials and in no way suggests expertise in metallurgy.

 

I’ve thought something very much like this. I’ve been rather skeptical of the tall tale used to explain the coin.

 

The “tall tale” I described is much like what @GDJMSP described. Something hit the coin hard and caused a pre-existing planchet flaw to break apart.

 

Thats amazing. Love the storied display

 

Good job inspector. Digging that out

 

Awe man. I hope all your coin ain't like those

 

I'm sticking to @TypeCoin971793 story. I think he thunk alot alot before his hippopotamus

 

Coolness

 

I'm just glad it was. Maybe Peter loved typecoins hippopotamus

 

That gets my best answer