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Author Topic: Belgium: 10 centimes 1944 with warts  (Read 191 times)

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Offline FosseWay

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Belgium: 10 centimes 1944 with warts
« on: September 09, 2017, 11:24:20 AM »
Can anyone shed any light on the origins of the warts on the reverse of this coin?

As you can see, it is broadly in pretty reasonable condition, and the other side is unblemished. I doubt it's been lying around in the damp or whatever for any significant time.

As far as I know these are made of solid zinc - they're not plated, so it can't be bubbles/imperfections under the cladding as you see on modern euro and sterling "coppers".

Offline Globetrotter

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Re: Belgium: 10 centimes 1944 with warts
« Reply #1 on: September 09, 2017, 06:22:29 PM »
Hi,
please see this Austrian coin, it's the same "disease"
Ole
Ole

If you're interested in coin variants please find some English documentation here:
https://sites.google.com/site/coinvarietiescollection/home
and in French on Michel's site (the presentations are not the same):
http://monnaiesetvarietes.esy.es/

Offline FosseWay

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Re: Belgium: 10 centimes 1944 with warts
« Reply #2 on: September 09, 2017, 09:51:31 PM »
Mange tak Ole  :)

Seems slightly strange though that it should affect one side so comprehensively yet the other side is entirely free.

Offline Globetrotter

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Re: Belgium: 10 centimes 1944 with warts
« Reply #3 on: September 10, 2017, 01:25:36 AM »
Det var saa lidt.

http://www.coinworld.com/news/us-coins/2012/11/occluded-gas-bubbles-can-be-mistaken-for-die-.all.html

quote:
 Occluded gas bubbles

The only remaining possibility is that these are occluded gas bubbles. In this rare planchet defect, heat generated by the strike causes a pocket of gas to form and expand below the surface of the coin.

An “occluded” gas bubble is simply one whose roof has remained intact instead of rupturing from the internal pressure. If the roof is of sufficient thickness, it could conceivably resist pressure from a toothpick.

The occluded gas bubble hypothesis is supported by a microscopic surface texture that is identical to the surrounding field. Even microscopic die flow lines continue across the two bulges without interruption. This supports the idea that the die face was intact and undisturbed when the coin was struck.

Occluded gas bubbles are restricted to solid-alloy coins and should be distinguished from plating blisters that form in copper-plated zinc cents. Blistered plating occurs when there is a poor bond between the copper plating and the zinc core. Heat generated by the strike causes gas expansion beneath the plating, pushing it up. Several unusually large blisters are seen in the accompanying 1986-D Lincoln cent.

I recently acquired an example similar to the 1949 cent that would seem to break the logjam of competing hypotheses. The illustrated 1958-D Lincoln cent has a much larger elevation located in the field above the date. Its relief is similar to the two elevations seen in the 1949 cent. Like that cent, there is no change in microscopic surface texture and the margins of the mound are soft. As with the previous example, the bulge failed to flex when pressed with the tip of a toothpick. The color is natural and no damage appears on the reverse face.

Although I wasn’t able to produce flexion or an indentation in the surface of the mound, a stronger impact received during its years of circulation managed the task. A microscopic transverse crease/scratch crosses the apex of the mound. Above and below the crease, the surface of the mound is warped subtly downward, indicating that the mound is probably hollow.

The perfectly normal reverse face provides another clue that this elevation formed at or after the strike. Any recess in the die face this broad and deep should have caused at least a little bit of weakness on the opposite face. The totality of the evidence indicates that this elevation is probably an occluded gas bubble.

By extension, I now believe that the two elevations on the 1949 Lincoln cent are also occluded gas bubbles.

My previous experience with occluded gas bubbles involved much smaller blemishes, as on the reverse face of the illustrated 1941-D Winged Liberty Head dime. Here a circular bubble has pushed up the M of AMERICA and the adjacent field. Its status as a gas bubble is confirmed in the lower half of the reverse face, which shows many fine linear gas bubbles.


http://www.error-ref.com/gas-bubbles/
Quote:
Gas Bubbles
PART V. Planchet Errors:
Alloy Errors:
Gas Bubbles

Definition: On rare occasions a pocket of gas forms and expands when a planchet is struck. The heat generated by the strike is deemed responsible for the gas expansion.  The expanding gas pushes up the overlying metal, producing a rounded bulge with soft borders.  If the roof remains intact, the error is designated an “occluded gas bubble”.  If the roof explodes from the internal pressure, we call it a “ruptured gas bubble”.

If the roof is thin, it will flex or it will be left with a dimple when the tip of a toothpick is pressed into it.  If the roof is thick, it may not yield to pressure.

By definition, occluded gas bubbles are generally restricted to solid-alloy issues.  While gas bubbles are sometimes seen on clad coins, these always turn out to have been caused by heat applied externally outside the Mint.  Occluded gas bubbles should not be confused with blistered plating, the latter being an affliction restricted to copper-plated zinc cents.

A 1986-D cent with blistered plating is shown in the above images.  The blisters are unusually large.

The next set of images are of a 1958-D cent with a large occluded gas bubble above the date.

The last set of images show a 1949(P) cent with two occluded gas bubbles seen to the left of Lincoln’s bust.


Etc, etc, just google "occluded gaz bubbles!

Ole
Ole

If you're interested in coin variants please find some English documentation here:
https://sites.google.com/site/coinvarietiescollection/home
and in French on Michel's site (the presentations are not the same):
http://monnaiesetvarietes.esy.es/