South Korea 10 Won 1970 KM#6 or KM5a (How to see the difference?)

km6
https://en.numista.com/catalogue/pieces2646.html
km6a
https://en.numista.com/catalogue/pieces2796.html

My coin
km6?

Coin in numista km6a?


If the images are correct it's very difficult to distinguish the two. I had hoped it would have been like for the 5 won coin km5 and 5a as discussed here https://en.numista.com/forum/topic113023.html#p929981 , where in the end the "7" can determine the km#, but here it's maybe not the case? If the images are wrong, you know.

Can anybody help, please?

I could distinguish the difference right away, subtle, but there in this example comparing the two in my opinion. Perhaps some cannot see it. Color/tone/yellow/red/light/dark/brass/bronze. Verbiage. It clearly cannot be used exclusively as a determining factor but can certainly be used as clue as to the composition of a particular variety in many cases. It's the first thing you see without getting into the finer details. That's my story and I'm sticking with it.

In my opinion, both coins are KM# 6a. Explanation follows later this evening.

It took me longer than expected, but here it is.

Ole, you're focusing on the wrong subject. Just like for the 5 won the main focus should be on the composition. KM# 6 is bronze, KM# 6a is brass. They both have typical characteristics: bronze is reddish/brownish, brass is yellowish. They are different alloys so there also might be a difference in weight. Don't always count on the data provided in Krause or in our data sheet (we often take over mistakes occurring in Krause) but do the measurements yourself. Measuring is knowing.

Measurements:



When we order by Diameter or Thickness, there's no pattern and the data in Krause and Numista are acceptable:



But when we order by weight it's a different story:



Although the difference in average weight is little (4.02 for the brass coins, 4.19 for the bronze coins), it can't be a coincidence that ALL bronze coins are on top of the list!

Colour:

Look at all the dates one by one. You'll see the first 4 are all KM# 6 and they are all reddish/brownish. All the following ones are KM# 6a. Some are darker, some are lighter, but they all have one thing in common: they all are yellowish:



When you place them randomly on the scanner you can easily pick up the bronze KM# 6 ones, just by their colour:



Even when you look at the edges only, you can point out the 5 bronze coins easily. If this all isn't convincing I don't know what is:



In the photo gallery above the two coins where it's all about are missing: the 1970 bronze KM# 6 and the 1970 brass KM# 6a. Here they are:



Conclusion:

Don't look at differences in the shape of the 7 or stuff like that. Just loot at the colour of the coin and the weight. Ole, as for your coin in your original post: your coin is yellowish, so it's the brass KM# 6a. Let us know the weight of that coin, I'm sure it will be under 4.13 g.

By the way, the same story applies for the 5 Won. That 7 thing is a date thing, not a type thing. To determine the type you also have to look at colour and weight. This also means your documentation for the 5 Won is WRONG. You should exchange the KM# 5 and KM# 5a on your documentation there.

Hi Essor Prof,

I see what you mean, but please explain to me, why the "7" are different for the km5 and km5a. It seems it's contradicting your findings. I cannot forget that, because it's also findings.

On the other hand I have a conflict here with the 1970 coin:

Maybe I should have another look at my 1970 coin tomorrow, specially at the "7"

Oh, my, what a coin?

Verweis : "Sjoelund"​​On the other hand I have a conflict here with the 1970 coin:
​

​Maybe you haven't. Maybe you've made the wrong assumption based on your incorrect 5 Won documentation. If you have assumed your coin is a brass coin based on the shape of the 7, you assumed wrong and your supposedly brass coin is in fact a bronze coin and then the weight fits perfectly in your list. I'd like to see a picture of your 1970 5 Won coin. I also like to know the weight of your 1970 10 Won coin on your first post in this topic.

Verweis : "Sjoelund"​I see what you mean, but please explain to me, why the "7" are different for the km5 and km5a. It seems it's contradicting your findings. I cannot forget that, because it's also findings.

​I never said to use the shape of the "7" to determinate the type. I said to use the shape of the "7" to determinate the type within the 1970 coins. That's a big difference. You started to compare the "7" within different dates and took the wrong conclusion.
Look carefully at the 10 Won coins. Almost every date has some small differences, although they all are the same type KM# 6 or KM# 6a. These differences are a date thing, not a type thing.
For instance:
For the KM# 6:
- 1966: Date starts right in the middle of K, narrow date.
- 1967: Date starts under the second leg of K, narrow date.
- 1968: Date starts under the first leg of K.
- 1969: Date starts under the first leg of K, wide date.
- 1970: Date starts under the first leg of K, narrow date.
For the KM# 6a:
- 1970: Large 7.
- 1971: Small 7, 9 with small hole.
- 1972: Date starts immediately under KOREA.
- 1973: Wide date.
- 1974: Narrow date.
- 1975: Wide date.
- 1978: Date starts left under K, narrow date, oval hole in 9.
- 1979: Thin date.
- 1980: Big holes in 9 and 8.
- 1982: Small holes in 9 and 8.
So don't look for differences in the date to determinate the type!

So this is my 10 won coin, I measured it again and found the following.
W 3.95 D 22.89
I probably got a better coin at some time and didn't bother to check, sorry.

Like I predicted your coin would be under 4.13 g. With that weight and that colour, your 10 won coin is definitely the brass KM# 6a, not the bronze KM# 6.

I have 2 of these coins. One from 1970 which I had cataloged as a KM#6 and a 1978 KM#6a. The 1970 weighs 4.00g and the 1978 weighs 4.09 g.


I should probably change the KM#6 to KM#6a. Agree?

No. The problem with the weight is that the average weight of the bronze coins and the average weight of the brass coins is very close to each other, a difference of about 0.2 g. But we also have the factors tolerance and wear. Your coin definitely has some wear so it's not surprising your coin weighs less than average and the result falls into the weights of the brass coins. Let's say that the weight works in one direction only: you probably won't find any brass coins in the top of the weight list, but because of the combination wear and tolerance you'll find bronze coins lower in the weight list, between the brass coins.
But one thing doesn't lie for your coin and that's the colour: it's brownish/reddish and certainly not yellowish so your 1970 coin is indeed a KM# 6.

Thanks. Yes, that makes sense.