1967 Canada Commemorative 10 Cent Coin--80% vs 50% silver [solved]

In the Numista catalog:

KM#67 (80% silver) in the comments section:  “There exists also the variant of this coin with 50% silver that weighs 2.18 grams.”

KM#67a (50% silver) in the comments section:  “There also exists a variant of this coin struck in 80% silver with the same weight.”

Both of these statements cannot be correct.  

Both coins are listed with a weight of 2.33g.  They are both also listed as 18.034mm diameter and 1.21mm thickness.  My thought would be the 50% silver coin would weigh less if all other dimensions are the same but other online sites report that they both weigh the same.

From the same RCM link referenced by Québécois in this post about the 25 cent .800/.500 silver coins, there were no .500 silver 10 cent coins minted in 1967.

https://www.mint.ca/en/discover/canadian-circulation/10-cents 

The Canadian mint doesn't seem to list 50% 10 cent. 

https://www.mint.ca/en/discover/canadian-circulation/10-cents

1920 – 1967

Composition: 80% silver, 20% copper
Weight (g): 2.33
Diameter (mm): 18.034
Thickness (mm): n/a

1968 – 1977

Composition: 99.9% nickel
Weight (g): 2.07
Diameter (mm): 18.034
Thickness (mm): 1.16

For the scientific in you:

First method to difference 1967 RCM .500 from .800 coins:

Specific gravity can be measured accurately by use of sensitive laboratory equipment. For the average rockhound a good estimate of SG can be obtained by use of a rigged balance system. If the mineral can be weighed first dry, D, and then weighed, W, while emersed in a liquid, usually water, then the SG can be obtained by the following formula: SG = D/([D-W]L), where L is the density of the liquid, if water is used, L=1, so that the formula is simply D/(D-W). The mineral being tested must be homogenous and not contain other minerals. It is best to test single small crystals that are not attached to a host rock. (site http://www.galleries.com/minerals/property/density.htm

Silver 0.800: d = (0,800 x 10,50g/cm3) + (0,200 x 8,96 g/cm3) = 10,19 g/cm3
Silver 0,500: d = (0,500 x 10,50g/cm3) + (0,500 x 8,96 g/cm3) = 9,73 g/cm3

You could use the second method consisting of an un fluorescence-X analyser (witch cost $$$$ in the 4 digits).

The method described in point 1 will take you at a minimum of 1 hour of work, a good scale and 17 coins.

So I think unless members here have a coin in their possession and a proof of a difference in weight, I would leave the .500 silver 10 cents the way the RCM listed it. Same with the 25 cent.

Even if I don't agree and have no proof that the weight difference is proven, let's rely on the mint records, at least for this.

Best regards,

Québécois

…I would leave the .500 silver 10 cents the way the RCM listed it.

 

Except the problem is that the RCM doesn't list a .500 silver 10 cent coin.

Is the density test reliable?

According to your calculations the density of .800 silver is 10,19g/cm3 and the .500 is 9,73 g/cm3.

That is a difference of 0,56g for 1 cm3. The coin weighs 2,33g? So that's about 1/5th or 1/4th of the mass so you can divide 0,56 also by 4 of 5… That would give you a difference of 0,14g (or less) for a .800 or a .500 silver coin… Surely this is too small to be statistically significant? Even more so if you have circulated and worn coins...Or am I wrong?

Here is an interesting discussion from 10-12 years ago:

https://www.coincommunity.com/forum/topic.asp?TOPIC_ID=60503&whichpage=1

Newtony

Is the density test reliable?

According to your calculations the density of .800 silver is 10,19g/cm3 and the .500 is 9,73 g/cm3.

That is a difference of 0,56g for 1 cm3. The coin weighs 2,33g? So that's about 1/5th or 1/4th of the mass so you can divide 0,56 also by 4 of 5… That would give you a difference of 0,14g (or less) for a .800 or a .500 silver coin… Surely this is too small to be statistically significant? Even more so if you have circulated and worn coins...Or am I wrong?

Yes, if done carefully.  There can be a lot of experimental errors if you're sloppy.  A tiny air bubble will throw off the results.  The tests should be repeated several times.  Here's a post where I did just this and could distinguish density difference is large coins (easier) and small coins (harder).  https://en.numista.com/forum/topic109244.html

Circulated and worn coins play no part in the results.  Density of a single material does not depend on the amount of material.

I solved the problem and marked mine as 65%.  😁

I don't want to delete the coin from the Numista catalog since it's such an emotional topic for some members and I will leave it at 2,33g at least for now.

Regards,