thickness and alloy in numismatic coins
 

Hi guys,

I've been looking for that for a while, and I can't find a good source of that information.

I'm looking for a database of thickness (not only diameter) of world coins (especially french), and their gold alloy.

I know that up to some date, french gold coins were alloy with silver, then some later dates look like some kind of copper/silver mix.

Also catalogs such as the krause only list AGW, not alloy, and neglect to list thickness as well.

Re: thickness and alloy in numismatic coins
 

I don't know any website with such comprehensive information, but if you have a good library nearby, check it out. Many of the annual World Coin Guides have much of the information you seek, as well as numerous other numismatic reference books.

Also, for anyone interested in world coins in general, http://worldcoingallery.com is a good place to start.

Re: thickness and alloy in numismatic coins
 

When in doubt, email the mint that struck the coin.

Alloy information is sometimes difficult to find.

Good luck.

Re: thickness and alloy in numismatic coins
 

Did you try http://www.coinflation.com/ ?

Re: thickness and alloy in numismatic coins
 

Thickness should be pretty standard. Are you talking about the old, common gold coins like roosters, helvetias, dutch dogs, etc., or are you also interested in rarer gold coins? Modern coins?

Regarding the alloys, you might have some luck checking into the government assay offices of the various countries you're interested in. Many mints submit their coins to a 3rd party or government assay or weights and measures office every year. It's often ceremonial, but many of these places still do check the alloys of the coins, especially gold coins.


I have tons of old coin books around here. I'll try to see what I can dig up regarding French gold alloys.

Also keep in mind that coins of the same alloy can tone differently, even when left in the same environment.

This information should be easier to find.

I love the metallurgical sciences, and I'm always curious about things like the annealing process, the alloy ratio, etc., but it's not easy to find this stuff.

Re: thickness and alloy in numismatic coins
 

I was a little slow this morning, so I analyzed a 20 Franc Rooster.

I took 3 readings. The machine is accurate up to 1/100th of a percent, these would be the approximate average.

Au 90%
Cu 9%
Ni 0.5 %

I used this machine:
http://www.helmut-fischer.com/Produc...1&LanguageID=2

Re: thickness and alloy in numismatic coins
 

21.6K (0.900) 1.4mm thick. Very hard to find out the alloy, all anyone seems to care about is the gold content. It would seem to be 0.9 gold, 0.1 copper, but I'd take the actual measured reading over the "official" number.

Re: thickness and alloy in numismatic coins
 

Wow, the least I can say is that you're well equipped!

You got other gold coins that you tested for alloy content?

Re: thickness and alloy in numismatic coins
 

I started to be interested by the topic when I got two french gold coins from the beginning of the 19th century, a 20F 1818 and a 40F 1830.

The 1818 one looks yellowish, as if it's silver alloyed, while the 1830 one looks more orange, but not quite like a sovereign. Note that they are .900 gold instead of .917 like the sovereign.

So I was wondering if there was some change in the alloy at some point or not.

Re: thickness and alloy in numismatic coins
 

I have an old Alan Herbert book that mentions this topic, and what he says corroborates Montecristo's numbers.

And if I remember correctly, the US Mint has played around with alloys more than its European counterparts. For example, some US gold coins that were supposed to have been .900 fine gold have turned out to be .89 fine. They've been loose with their copper penny alloys, too. But I digress.....

The old European mints were less cavalier from what I've read. When it comes to gold coins from Europe, the general rule of thumb is that silver-gold was the alloy of choice for ancient coins, and copper-gold has been the alloy of choice in modern coinage. The little bit of nickel makes sense, too, to add some durability. I'm no expert, so don't hold me to any of this.


Montecristo's numbers are probably as good as any.

Very interesting, topic, btw. Wish I knew more!