Mexico 5 centavos 1965 Copper-Nickel KM# 426a 0

[kostj]

Hello, Is it brass or copper-nickel coins? 

 

[RWB]

Can't determine anything from the photos. Need weight, edge photos, etc., etc. Specifications say brass, weight of 4 grams. Correcting for color balance also supports brass. How could this be mistaken for CuNi alloy?

Edited September 7, 2021 by RWB

[kostj]

The problem is the brass and copper-nickel coins have the same weight, diameter and edge.

[RWB]

On 9/7/2021 at 3:56 PM, kostj said:

The problem is the brass and copper-nickel coins have the same weight, diameter and edge.

They have a different color... CuNi will look like a 5-cent nickel coin in color. Also, the density will differ. The density of Cu 75 Ni 25 is 8.95; common brass, Cu 80 Zn 20 is 8.59 g/^3 cm.

Edited September 7, 2021 by RWB

[kostj]

Thanks. Your color correction is wrong. The coin looks the same as on the display i.e. look like a 5-cent nickel coin. CuNi and brass coins have weight 4 grams. Different catalogs specified diameter both coins 20.4 - 20.5 mm.
How can density be determined? 

[gmarguli]

A quick acid dip will turn many red copper coins to gray. Very possible that is what was done here. Look at the reverse of the last pic. There is some red creeping through.

[RWB]

On 9/7/2021 at 5:01 PM, kostj said:

Your color correction is wrong.

I assumed your background was off-white - or something similar. The color of the original image background is light blue.

You can find instructions for measuring the density ("specific gravity") on the internet.

[Henri Charriere]

[I absolutely, positively refuse to believe anyone of @gmarguli's stature would even entertain a thought involving an "acid dip," quick or not -- and coins.  Whomever hacked this long-standing, seasoned veteran's account owes him and the membership an apology!]

[kostj]

On 9/7/2021 at 11:25 PM, RWB said:

They have a different color... CuNi will look like a 5-cent nickel coin in color. Also, the density will differ. The density of Cu 75 Ni 25 is 8.95; common brass, Cu 80 Zn 20 is 8.59 g/^3 cm.

The difference in density is very small.
The density of 5 centavos 1965 Cu 75 Ni 25 is 8.92; brass, Cu 85 Zn 15 is 8.66 g/^3 cm.
The difference is near 0,01 g for coin. I don’t have such precise instruments. 

Check out comparative photos. 

 

 

[kostj]

On 9/8/2021 at 2:02 AM, gmarguli said:

A quick acid dip will turn many red copper coins to gray.

Brass does not turn to gray. Check out the photo from the last post. 

[EdG_Ohio]

According to NGC's World Coin Price Guide it is :

Specifications
Composition: Copper-Nickel Diameter: 20.5mm
Design
Obverse: National arms, eagle left Reverse: Bust right

https://www.ngccoin.com/price-guide/world/mexico-estados-unidos-mexicanos-5-centavos-km-426a-1960-1965-cuid-1116306-duid-1427452

[Conder101]

I think your best course of action would be an XRF gun test.  If its plated and the test doesn't penetrate the plating the nickel content will read way too high.  If it is coppernickel you should get a reading of 75% copper 25% nickel. If it is plated brass and it DOES penetrate the plating then the ratio of copper and nickel will be important and whether or not there is zinc present and if so how much. 

[Henri Charriere]

@Conder101

[Deleted; I respectfully defer to @Conder101]

[VKurtB]

You can always revert to “The Beginner’s Gambit”; insist that yours is the more valuable version and grow ever more insistent over time. It’s an old approach, but a classic.