Making errors with bimetallic coins

[UK Decimal +]

I knew of the general theory behind it and suggested it to 'the expert'.   Aditya has explained the details in a way that is easy to understand.

My full theory is that someone might have heated the coin and then cooled the inner pill using 'dry ice' to shrink the centre.   This would create a greater difference in sizes between the heat-expanded outer ring and the ice-contracted inner pill.

Just a possibility, but a version of something done in industry more often than the public would realise.

Bill.

[andyg]

My full theory is that someone might have heated the coin and then cooled the inner pill using 'dry ice' to shrink the centre.   This would create a greater difference in sizes between the heat-expanded outer ring and the ice-contracted inner pill.

I think there may be an easier way,
I would start with two coins then drill out the middle of one, and remove the ring from the other.
Providing the centre of the first coin was still a tight fit in the ring of the second coin, it could simply be hammered back again using a piece of wood to guard the surfaces.

[Bimat]

I agree with Bill.Such a huge change in structure is possible only when there's a large temperature fluctuation.Even if the temperature in UK goes down to -30⁰C,there will be a little change.Dry ice will bring down the temperature to -70 to -80⁰C,and then if you heat it to 200-250⁰C in an oven,there will be a great change in structure (like this).

Aditya

[Bimat]

I would start with two coins then drill out the middle of one, and remove the ring from the other.
Providing the centre of the first coin was still a tight fit in the ring of the second coin, it could simply be hammered back again using a piece of wood to guard the surfaces.

There is a little possibility that this will happen.You need to apply great pressure (several kilo pascals) to make sure that rings don't separate,and no one can have those devices to achieve such a large pressure difference..

The worst I've experienced was -23c in Berlin in 1979. The winter temperature on the UK mainland gets nowhere near that in the cities and towns.

For a Mumbaikar,-23C is dreamlike.The worst winter we ever had was in 2007,when temperature was as low as 80C 

Aditya

[andyg]

Here's one I made just now

If it weren't so cold and rainy outside I'd fetch a hammer (I just hit it with the end of a screwdriver), but even so the middle is quite solid and won't fall out any time soon.

[Figleaf]

Kon Tiki strikes again. Proving your point by doing it. Bravo. You can recuperate your cost by offering your newly made error on eBay.

When you have recuperated your hammer, could you fix our back door, please? It closes a bit too well.

Peter

[andyg]

Here is the finished (hammered) article.

Bids start at just 99p, Gentlemen please, for this very rare error coin.

[RHM22]

I will bid £5,000. I won't pay, but I'll bid.

[Bimat]

Mine is £9999.99
Is there anyone who is still willing to place a bid?

Aditya

[RHM22]

I will bid 9 Kenyan shillings!

[Bimat]

I will bid 9 Kenyan shillings!

One Billion ZWD from my side

Aditya

[asm]

In coin....?

Will you pay shipping?

Amit

[andyg]

Here is the final word on the subject,
It's a UK £2 coin where the middle is slightly off centre - thus proving that the original coin has been tampered with. (part of the silver centre design (top right) extends into the gold ring.)

[Figleaf]

I would agree that this piece is conclusive evidence that pill and ring are struck together. Thanks AJG.

Peter