Author Topic: 1982 20 Pence - Off Metal Strike (OMS)  (Read 477 times)

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Offline Director

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1982 20 Pence - Off Metal Strike (OMS)
« on: April 03, 2020, 01:40:43 PM »
Hello folks:

I came across a 20 pence in copper (probably) as opposed to the usual copper-nickel. If anyone knows the story behind this and an approx value, I would highly appreciate it.

Are these common? Are these rare? Are these real/fake? Couldn't find much online.

Please fire away!

Thank you, kindly.

Offline Alan71

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Re: 1982 20 Pence - Off Metal Strike (OMS)
« Reply #1 on: April 03, 2020, 06:46:24 PM »
Although 20p coins are cupro-nickel, they have a higher density of copper than other UK cupro-nickel coins.  I can’t remember the exact ratio but the 50p (and older 5p, 10p) have a ratio of 75:25 in copper’s favour.  I tried to google the 20p but couldn’t find it, but it’s definitely over 80% copper.  As I understand it, it has the highest amount of copper it can possibly have without having a copper colour.  However, even newly struck ones do not have the same “silver” colour as other cupro-nickel coins.

It’s therefore possible that yours is just an old coin where the copper is now showing much more prominently.  It could be a genuine error but I don’t know.  If it was made of the 1p or 2p alloy of the time (bronze) it would have had the copper colour from the start and would surely have been noticed?

It’s the oldest possible date for this coin so has seen 38 years of circulation - 20p coins don’t age well in terms of colour.

Offline Figleaf

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Re: 1982 20 Pence - Off Metal Strike (OMS)
« Reply #2 on: April 03, 2020, 09:33:14 PM »
Maybe this coin was kept in a high sulphur environment, like highly polluted air, for some time? The yellowish colour of the edge lettering seems to indicate sulphur. Copper comes in many colours, from red to brown to almost black, but not this yellow.

Peter
An unidentified coin is a piece of metal. An identified coin is a piece of history.

Offline SandyGuyUK

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Re: 1982 20 Pence - Off Metal Strike (OMS)
« Reply #3 on: April 04, 2020, 11:22:25 AM »
Although 20p coins are cupro-nickel, they have a higher density of copper than other UK cupro-nickel coins.  I can’t remember the exact ratio but the 50p (and older 5p, 10p) have a ratio of 75:25 in copper’s favour.  I tried to google the 20p but couldn’t find it, but it’s definitely over 80% copper.  As I understand it, it has the highest amount of copper it can possibly have without having a copper colour.  However, even newly struck ones do not have the same “silver” colour as other cupro-nickel coins.

It's 84% copper and 16% nickel.  :)
Ian
UK

Offline FosseWay

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Re: 1982 20 Pence - Off Metal Strike (OMS)
« Reply #4 on: April 04, 2020, 04:06:03 PM »
The East Germany 5 Mark coin to commemorate the state's 20th anniversary in 1969 was issued in a variety of proportions of copper and nickel. The very coppery-looking one is 90-10; the more silvery one I'm less certain of.

Offline FosseWay

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Re: 1982 20 Pence - Off Metal Strike (OMS)
« Reply #5 on: April 04, 2020, 04:08:09 PM »
Could the OP's 20 pence coin have been subject to some form of, um, aftermarket enhancement, such as being electroplated?

Offline africancoins

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Re: 1982 20 Pence - Off Metal Strike (OMS)
« Reply #6 on: April 04, 2020, 07:18:13 PM »
I think I remember seeing this sort of variation in 20 Pence coins when pieces of the earlier type (that shown) were new in circulation.

I do not seem to have one now though.

The more recent 20 Pence pieces always seem to quite silvery and bright....  though not a match for the 5p and 10p coins.

The Republic of India 2 Rupees KM-121.x in Copper-Nickel also come in a few different shades... this is linked a bit to the date/mint/etc..

Thanks Mr Paul Baker

Offline Henk

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Re: 1982 20 Pence - Off Metal Strike (OMS)
« Reply #7 on: April 07, 2020, 01:40:33 PM »
If it is a genuine off metal strike one expects  it would have been struck on an other planchet. This likely would not have been a 7-sided one. It is a bit difficult to see from the photo but the coin looks a bit circular on one side.
Is the shape and size of the planchet identical to that of a normal 20 p coin? (Diameter is 21.4 mm and thicknes 1.7 mm)
What is the weight of the coin? (official weight is 5.0 g)
Is it attracted by a magnet? (A copper nickel one is not)
 
Answering these questions may help to determine if it is off metal or discoloured

Offline Alan71

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Re: 1982 20 Pence - Off Metal Strike (OMS)
« Reply #8 on: April 07, 2020, 09:52:40 PM »
^^ 1p and 2p coins did not become magnetic until the change to copper-plated steel in 1992.  In 1982 they were still bronze and non-magnetic.  Therefore the magnet test wouldn’t prove anything. 

20p coins have quite rounded angles anyway.  There are still angles visible on this, though the top of the coin is rounder than it should be (however, this could be signs of wear).

Offline Seeker55

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Re: 1982 20 Pence - Off Metal Strike (OMS)
« Reply #9 on: April 07, 2020, 10:32:06 PM »
Interesting discussion. Just for the record, while elemental sulfur itself is yellow, sulfides of copper are generally blue or black.

Offline Henk

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Re: 1982 20 Pence - Off Metal Strike (OMS)
« Reply #10 on: April 10, 2020, 02:45:46 PM »
^^ 1p and 2p coins did not become magnetic until the change to copper-plated steel in 1992.  In 1982 they were still bronze and non-magnetic.  Therefore the magnet test wouldn’t prove anything.

Yes, thohgh about this. But the planchet used could have been foreign. If the coin is magnetic then it certainly is an off-metal strike.

If it is not magnetic and weight and diameter are within specification of a 20 p coin I assume it has been plated. This can be tested by scratching a tiny bit from the edge.

I will be interested to hear the results of the measurements and, if needed, the result of the scratch test.

Offline Director

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Re: 1982 20 Pence - Off Metal Strike (OMS)
« Reply #11 on: April 11, 2020, 12:18:27 PM »
Hello again,

The weight is 3.8 grams, could be 3.7 something as it’s rounded up on the scale.

It seems to me it’s struck on a 1982 penny bronze blank (3.56 gms) or a foreign blank. I am leaning towards a penny blank as the weight is very close to that, but still would send it off for grading ASAP to rest my case.

After seeing the photo below, environmental toning is completely out of the picture IMHO.

See attached and once again, fire away!

Thank you and stay safe!

« Last Edit: April 11, 2020, 01:44:21 PM by Director »

Offline Henk

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Re: 1982 20 Pence - Off Metal Strike (OMS)
« Reply #12 on: April 11, 2020, 12:32:02 PM »
The specification of a 1p coin is:
Diameter   20.3mm
Weight   3.56g
Thickness   Bronze: 1.52mm

So it may indeed be struck on the planchet of a 1p coin. As a further check you could measure the thickness and also check your scales by weighing a 1p coin and a 20p coin.

Offline Director

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Re: 1982 20 Pence - Off Metal Strike (OMS)
« Reply #13 on: April 12, 2020, 12:07:14 PM »
The specification of a 1p coin is:
Diameter   20.3mm
Weight   3.56g
Thickness   Bronze: 1.52mm

So it may indeed be struck on the planchet of a 1p coin. As a further check you could measure the thickness and also check your scales by weighing a 1p coin and a 20p coin.

Yes, indeed. Thank you for your help!