Expanding Billon and Electrum [solved]

Hello!

Currently, in our guidelines, we have this:
- "For coins containing less than 50% silver, select “billon silver” and specify the silver content in the additional details field"
- "For coins containing less than 50% gold, select “gold” and specify the fineness"

The problem with the first guideline is that we do not have a "billon silver" composition. The problem with the second guideline is that... well, when do we use electrum?

I understand why, if gold is below 50% purity, we should still select gold as the composition--gold is a very valuable precious metal, and this way, we can display the proper melt value. But electrum is still a precious metal... perhaps there could be a way to select Electrum and still display the exact melt values?

I am thinking something like this:


Total melt value would be x = (value of gold)*(fineness of gold)*(weight) + (value of silver)*(fineness of silver)*(weight)

Similarly, we could do something like this for Billon, with only a silver purity option:


Total melt value would be x = (value of silver)*(fineness of silver)*(weight)

Obviously, the melt value of a small coin with purity Ag .1875 is rather insignificant; however, the value of larger billon coins might be of interest to some people, and we would have a way to standardize the purity comments of billon coins (which, I imagine, could really use some standardization).

For example, if you were to type in the above purity in the Silver fineness field of Billon, you could see it like this on the coin page:
https://en.numista.com/catalogue/pieces141924.html
[That is how I would like to see it, at least--there are many other ways to do it.]

The same thing would happen with Electrum--while we do not have many electrum pieces with a specified purity on Numista, that could very well change (it looks like those of Carthage have known purities, for example). And an example this would help can be found here:
https://en.numista.com/catalogue/pieces102134.html (again, the format of the purities could be standardized by implementing this feature).

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Ideally, I would like to see a way to standardize all purity comments, but... this should at least cover the biggest precious metal ones. And... yeah. Thoughts on this?

Hello,

 

It's now possible to enter the silver fineness for billon coins.

This will be reflected on the coin page as “Billon (.156 silver)” for example and the melt value is computed.

 

See for example N#143431 

 

The guidelines have been adjusted: “For coins containing less than 50% silver, select “billon” and specify the silver content in the fineness field”.

 

Ideally, we should have more detailed fields for all alloys (including electrum), in order to specify the exact composition and percentages. It's not a priority at the moment.

Personally, I would keep electrum for those ancient coins that were made from the natural mineral. Because of the nature of things the metal content varies and unless you test each particular coin we wouldn't know for sure. If it's a manmade alloy with a fixed mixture I would keep it as gold (XXX) [I think it's called “green” gold] stating somewhere that the biggest alloy partner is silver.

I agree we should keep electrum. Perhaps we should modify the guidelines to make them more explicit. I'm not sure how to avoid all ambiguities, to differentiate electrum (example: stater from Kysikos) vs white gold (example: centre of the Montesquieu coin, made of gold .750, palladium  .150 and silver .100) vs debased gold (example: provisional coin from Oaxaca, made of gold .175). The sentence in the guidelines (“For coins containing less than 50% gold, select “gold” and specify the fineness”) refers to this last category.

 

A few examples of coins currently categorized as gold with less than 50% gold:

N#232865 Gold .375

N#15033 Gold .175

N#63904  Gold .4166

N#287358  Gold .344, silver .639 (should it be changed to electrum?)
N#69472  Gold .229 (electrum?)

N#277266 Gold .024

N#198424 Gold .333

 

 

By the way, I modified all the coins indicated as “silver” and changed them into “billon” when the fineness was below 50%. We now have 45% more billon coins in the catalogue.

All the older Japanese “gold” coins were made with specific alloys and acid treated to appear more golden despite their lower gold content.

So I wouldn't call them electrum but I could live with it if we decide to use it for all sub 50% alloys to make things easier.

Xavier

By the way, I modified all the coins indicated as “silver” and changed them into “billon” when the fineness was below 50%. We now have 45% more billon coins in the catalogue.

and 234 of them are still in use according to our catalogue … mainly in France (€10 non-circulating coins !), but in reality probably most in US (5 cents 0.350 and half dollars 0.400) [should all non-circulating coins not be automatically marked unknown as per guidelines?]