How to tell the difference: South Korea KM#6 vs KM#6a

South Korean 10 Won coins dated 1970 were made from both bronze (KM#6) and brass (KM#6a). When this comes up with other coins it's normally easier to tell the difference, but I'm having trouble with this one. I have three dated 1970 and am comparing them against a couple dated 1967 (KM#6 / bronze) and several dated after 1970 (KM#6a / brass), but even when comparing those two groups I can't tell the difference. Even looking at the photos in the links above, the three 1967's I have look more like the photos for KM#6a. Does anyone have any good methods for telling them apart?

Hi,

here are the documentations from Cobra concerning the the Korean 10 won coins. The French is easy to understand!


here for the later version


Maybe I ,should convert them into my usual form.

Ole

Comparing the color of the 1970 brass and bronze ones is not easy when the coins are patinated.
Is there any difference in the dies?

Цитата: "PetrusAscanus"​Comparing the color of the 1970 brass and bronze ones is not easy when the coins are patinated.
​Is there any difference in the dies?

​not my knowledge....

ole

As far as I know it is only a color test...i will ask some Korean collectors if they can tell. I have only ever used color test.

It is the same with 5 and 5a. I think if you have a circulated date prior to 1970 and a circulated 1971 or later and then compare your 1970 to each then you can be reasonably successful in your determination.

I've come to the same conclusion as PetrusAscanus -- it can be difficult once there is a patina. These photos show nine 10 Won coins. Two are in the range 1966-1969 (KM#6), five are 1971-1982 (KM#6a), and two are unknown from 1970. To keep it objective, only the obverse sides are shown.

No flash:


With flash:

Цитата​​No flash:​

In case anyone was curious, here are the dates dates and KM numbers of those in the photos:
71(6a) 79(6a) 67(6)
67(6) 70(unknown) 70 (unknown)
80(6a) 72(6a) 78(6a)

The 10-Won coins minted between 1966 and July 16, 1970 were minted with 88% copper, 12% zinc composition planchets. Alloys of around 90% copper, 10% zinc are called "Commercial Bronze" by the metals industry. This is NOT "Bronze," of course, but just a brass alloy. It's just a NAME for this brass alloy, and not an actual description of the metal. Real "bronze" contains tin, and this coin does not. I think that coin collectors latched onto this name and started calling these coins the "Bronze" variety. The Krause-Mishler (KM) number for these coins is KM#6.

The 10-Won coins minted after July 16, 1970 to 2006 were minted with 65% copper, 35% zinc composition planchets (although the design changed in 1983). Alloys of copper that have at least 33% zinc are called "High Brass" by the commercial metals industry. Again, I think coin collectors started using the name, "Brass" to differentiate this copper-to-zinc alloy percentage from the previous copper-to-zinc alloy percentage.

I got two of my 1970 dated 10-Won coins graded and XRF analyzed to determine which alloy they were, since the South Korean Mint struck the 10-Won and Five-Won coins that year using BOTH alloy percentages. There IS a color tone difference that you can often use to tell the difference for these 1970 dates, ONLY if they are in uncirculated condition. In circulated condition, it is much harder to tell. Both of my coins were the "Bronze" variety. See this video:
https://www.youtube.com/watch?v=do9CP5FWyJ0

Also, see this page:
http://dokdo-research.com/southkoreancoindata.html

Thanks for your information. That explains why it is so difficult to determine these two types by colour only.