Coin sizes.

[Bullionbilly]

In light of a recent topic regarding fakes i decided to purchace a pair of calipers to measure my coins aswel as magnet and weight test.

How exact do we go when comparing to the mints specs ?

Ive just checked 2 - 2oz kooks.

Coin 1 . Weight 62.7 size 49.90 thick 3.8.

Coin 2 . Weight 62.8 size 49.89 thick 3.7.

Mint says min of 62.27g 50.3mm/4.5mm

Both pass magnet test.

Do we expect absolutely bang on the specs quoted by the mint ?

 

 

[Pete]

4 hours ago, Bullionbilly said:

In light of a recent topic regarding fakes i decided to purchace a pair of calipers to measure my coins aswel as magnet and weight test.

How exact do we go when comparing to the mints specs ?

Ive just checked 2 - 2oz kooks.

Coin 1 . Weight 62.7 size 49.90 thick 3.8.

Coin 2 . Weight 62.8 size 49.89 thick 3.7.

Mint says min of 62.27g 50.3mm/4.5mm

Both pass magnet test.

Do we expect absolutely bang on the specs quoted by the mint ?

 

 

Weight should never be less but might be very close to the exact specification.
I actually have some genuine Pandas that are slightly underweight !!

Measuring thickness can be a problem as some coins will have a rim and depending on how the coin was stuck this rim can sometimes be slightly oversize.
This is particularly true with older gold sovereigns and using the thickness test passing through a slit would make you concerned when it didn't pass through due to the rim.
I measure coin thickness near the centre of the coin using a micrometer if I am suspicious.
Vernier callipers would measure the rim thickness.

As for the specifications - you need to check various sources as sometimes the sizes are figuratively stated or rounded.
There is an exact specification but it is not always stated on promotional pages.

A fake coin will be underweight and oversize, generally both.
It is too costly to produce an alloy that has the same density as silver and the nearest match to gold is tungsten but to make a coin out of tungsten would be a big challenge due to its hardness. Gold bars however can have tungsten rods buried inside and measuring the volume of a bar is likely to be inaccurate when it has rounded edges for example. The definitive test is specific gravity or proper high tech analysis.

[BackyardBullion]

2 minutes ago, Pete said:

The definitive test is specific gravity or proper high tech analysis.

I agree with the last point - a specific gravity test is just conclusive proof however you look at it. Only Tungsten gold can be close to the right SGT - but its just not worth it for fakers to do. Generally if its a silver coin from a good source with a correct SGT measure then its genuine silver!

[Bullionbilly]

Just done sgt.

Coin was 62.9g

When in water was 6g.

62.9 ÷ 6 = 10.48. 

So it passed this test aswel.

 

[BackyardBullion]

1 hour ago, Bullionbilly said:

Just done sgt.

Coin was 62.9g

When in water was 6g.

62.9 ÷ 6 = 10.48. 

So it passed this test aswel.

 

Its real, no doubt!

[sovereignsteve]

7 hours ago, Bullionbilly said:

Do we expect absolutely bang on the specs quoted by the mint ?

Every analytical test has an Inherent inaccuracy whether due to operator, instrument error, temperature etc. Sometimes these errors can compound to give significant imprecision. As far as we're concerned, the instrument with the most scope for large inaccuracy is the humble, cheap balance as I doubt anyone here uses analytical balances accurate to 4 decimal places.

This obviously has potential to impact on SG measurement, which is quite difficult to get right in non-ideal conditions. A problem with silver as it's SG isn't unique enough, there are other metals and alloys that could be passed off as silver. Unlike gold which is fairly unique as has been mentioned.

3 hours ago, Pete said:

This is particularly true with older gold sovereigns and using the thickness test passing through a slit would make you concerned when it didn't pass through due to the rim

Interesting as I haven't observed this. I am curious to know which years you're referring to. In my experience it's the more recent coins, especially proofs that have this problem.

[Roy]

'Every analytical test has an Inherent inaccuracy whether due to operator, instrument error, temperature etc.'

It's true. Every 6 months I pass my liver function test. Extraordinary. 

[sovereignsteve]

Just now, Roy said:

'Every analytical test has an Inherent inaccuracy whether due to operator, instrument error, temperature etc.'

It's true. Every 6 months I pass my liver function test. Extraordinary. 

Best laugh I've had for ages. I pass mine too, but I do my own

[Roy]

That's like 'insider' trading!