I imagine the heat treating process of the working dies would have something to do with all of this. I certainly am no formal expert on any of that, but logic would dictate that the center of the die would be more prone to weakness when the dies are quenched (it being the center of mass and that cooling or quenching would not take immediate effect compared to the outer portions of the die. I would think that cooling and hardening would be most effective in these other, outer areas,....plus while things are cooling down, the are prone to brittleness if shaken or bumped. I know this to be true from the exhast pipes or heat suppresion baffles on jet engines which are made of steel and titanium. Once my engines were shut down, it tooks 20 minutes to detect any cracks or fissures that might develop during the cooldown itself. This was an important inspection during post-flight. I've seen saltine cracker sized chunks litterally drop away from
these technologically superior exhaust manifolds.....not good when your trying to reduce your heat signature for follow combat missions).
Regarding the 1922 Peace dollar, it must at least had been experiencing the outer reaches of catastrophic die failure.
I'll have to examine those Indian coins closer. Those Rhino 25 p's are steel planchets.
From: Mike Diamond <mdia1@...>
Sent: Saturday, May 28, 2011 1:07 PM
Subject: [Error Coin Information Exchange] Re: Puzzling split die error...or is it?
Your Peace dollar shows a profusion of conventional die cracks, none of which run rim-to-rim or are wide enough to be considered a split die.
Some of your Indian coins may be showing die subsidence in association with split dies or retained cuds.
Back to the US coins. I'm thinking that the failure of the bilateral, radial, antipodal die cracks to pass through or meet in the center may be due to their entering a zone of softer steel where crack propagation is difficult. Subsidence would not occur without a zone of softer steel in the center of the die neck.
--- In firstname.lastname@example.org, jeff ylitalo <jylitalo@...> wrote:
> I haven't had the pleasure of examining many US coins with major cracks or splits as you have mentioned (to
say with conviction one way or the other).
> I did post images of that 1922 silver peace dollar a couple of years ago, it is littered with splits and cracks (retained interior die-breaks). However, I don't remember any real zones of subsidence associated with any of the cracks or splits on the obverse face (as far as a lack of design detail however, peace dollars are notorious for weak strikes). Those images are in the 'cuds, collar and split die' album here on ECIE.
> From: Mike Diamond <mdia1@...>
> To: email@example.com
> Sent: Saturday, May 28, 2011 7:30 AM
> Subject: [Error Coin Information Exchange] Re: Puzzling split die error...or is it?
> In a few cases the lack of details on the zone of subsidence is at least partly caused by wear. But the lack of details is also seen on uncirculated specimens.
> In some cases the loss of detail is due to insufficient striking pressure on this area. As the center of the die retreats, resistance to the impact of the dies declines. In other cases, the design itself loses its fine details. This is clear from those specimens in which the zone of subsidence is smooth and lacks the tumbling marks of the unstruck planchet.
> I do have one Lincoln cent in which there is a wide, unilateral radial die crack. I've seen others. But none of them showed a centralized zone of subsidence.
> --- In firstname.lastname@example.org, innff@ wrote:
> > Mike,
> > Nice work. One comment though. I do have a fractured die that
> > shows a crack from one pole to another, except for one small area that it is
> > missing from. Could the missing area be from circulation wear?
> > The area below the beaded necklace is the questionable spot.
> > BJ
> > In a message dated 5/27/2011 10:53:34 P.M. Eastern Daylight Time,
> > mdia1@ writes:
> > I can now confirm that this isn't a split die. The two wide die cracks
> > arising from opposite poles pinch out as they reach the zone of subsidence.
> > This is going to force a re-evaluation of many presumed split dies, at
> > least those in which the two
ends of the split vanish within a featureless
> > zone of subsidence. Unless the split is really wide, there may be no way to
> > tell if the split is continuous across the zone of subsidence or if it's
> > interrupted in the middle.
> > This may also lead to some new thinking about how splits and wanna-be
> > splits form. But I haven't connected the dots yet, other than noting a strong
> > association between split dies and die subsidence errors.
> > All I know is that undoubted split dies are even rarer than I once thought.
> > I'm going to be writing my musings up for Coin World.
> > --- In email@example.com_
(mailto:firstname.lastname@example.org) , "Mike Diamond" <mdia1@> wrote:
> > >
> > > I plucked this 1974-D split die error from the "nickels" section of
> > eBay. The fact it was posted there instead of in the "errors" section may
> > account for why I got it for 99c.
> > >
> > > _http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=260784598206_
> > (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=260784598206)
> > >
> > > The center of the reverse face appears to show a die subsidence (sunken
> > die) error. This is something that is commonly seen in association with
> > split die errors. Usually the affected area is devoid of both the design
> > evidence of the split. In the past I reasoned that there was insufficient
> > pressure for either to show up. But here the design is fully intact, albeit
> > weak.
> > >
> > > So where is the split? It's not traversing the center of the design, nor
> > is it bifurcating around the weakly struck area to circumscribe a low
> > plateau. The evidence would seem to indicate that this is NOT a split die.
> > Instead it looks like we have two wide die cracks that pinch out as they enter
> > the zone of subsidence.
> > >
> > > This may indicate that some of the split dies with die subsidence that
> > have been previously diagnosed are not split dies at all.
> > >
> > > Can any of you provide an alternative interpretation?
> > >