This.. Is cool! I don't believe it's an error, I believe it's PMD, perhaps dipped in liquid nitrogen in-order to break this coin in half.. Or maybe a really sharp fast moving blade? Eh, well, sadly, it's not an error IMO. Well... Perhaps actually, I mean, I just remembered the Broken Planchet error caused by an improperly mixed alloy.
PMD. It's a circulated coin. It wouldn't have circulated like that if it spent it's whole life like that. Where did you get it?
I don't know. But looking at the responses you received over on Facebook I believe you will get the same answers here. Some say error and others that it's not. Are you submitting it for attribution?
I’m hoping to hear from those who can use diagnostics to explain why or why not. Hopefully a few more seasoned folks can chime in here or there. I don’t plan to get it attributed by a TPG. It’ll stay as is in my collection.
So far Mike Diamond chimes in on Facebook and said it looks like a natural break. That’s a good sign. I’ll try to get more photos. I don’t see any indication of bending/warping that I’d associate with what @ToughCOINS suggested. Not saying you’re wrong, just that I don’t see it as conclusive.
To me it looks like a natural break. What I don’t get is the circulation wear unless it was a defective planchet and circulated before it broke, which is a possibility.
Being a nickel doesn't bother me in the wear department. Many nickels do not so to say "Show the stress cracks" until they have seen circulation and environmental type damage. For example I have a wartime nickel that is PCGS xf45 and is a clamshell error. It obviously circulated plenty before someone noticed that the coin was separating.
How did you come by it? We need @Fred Weinberg and @JCro57 and others to chime in. Logic tells me that, as stated by @Lon Chaney said, it wouldn't have made it far in circulation, but what if it was an improperly mixed alloy and the stress of being in circulation finally caused the two parts to separate? Okay, then why would the break edge show wear? So many questions. Please let us know any additional information you find on this.
Sounds like you don’t know who Mike Diamond is. https://www.error-ref.com/about-the-authors/ His opinion holds a smidge more weight than others’. That said, @ToughCOINS is the only one who had used diagnostics of the coin itself to explain his reasoning. The only issue I take with his explanation is that I see not bending/warping of the coin when looking at it through the side view. I would expect to see even a little if it were repeatedly bent until it broke. Where do you see that? What tool would cause a coin to snap in half? The circulation and damage are concerning. Not sure what to make of them. I purchased this in a lot of buffalo nickels someone was selling. I saw the half piece and knew I wanted it. The first two photos are cropped images of the seller’s photos.
There are what appears to be neatly serrated lines that could have been made by a large cutting edge. I don't know if it's anything like that or not, just going by what I can see in the pics.
I probably shouldn’t have used the word “bent”, as that implies noticeable deformation every time the coin was loaded. Since the 75/25 CuNi alloy is so hard, especially after striking, you really can’t see the bending take place, because it is so subtle. The planchet is very strong, but brittle. When it finally breaks, it does so rather abruptly, usually preceded by cracking that is difficult to see. The crack propagates each time the coin gets loaded. Within the crack the material mushrooms, especially at the edges where it is compressed the most, and leaves a dull worn look, as opposed to the naturally grainy look normally seen at the interior of the planchet.
