Singapore 1 cent 1990 Copper Plated Zinc coins?

I have two N#6686, at least they are dated 1990.

But they sure look like copper plated zinc and not bronze, i.e. like N#10646, which should only be dated 1991.

I can scrape the edge of one to check, but first I thought to ask for any comments.

Solid bronze and copper plated zinc coins definitely should not have the same values for weight, diameter and thickness. 

With the same dimensions, the zinc one should be about 18% lighter, if the weight would be the same it should be larger then the bronze one.

Agreed.

Size is the same for both of my coins, I get 15.9mm diameter and a thickness a little less than the 1.1mm.  Weight is essentially the same too, 1.251g and 1.252g for the two coins.

As you probably checked, the two 1 cent pieces in Numista list the same dimensions and weight.  My Krause/Mishler (to be fair, 1996) does not give size or weight.

From SCWC 46th edition:

Thank you both.

So, I am at 1.24g and dated 1990.

It must be that some copper plated zinc coins were made in 1990. 

For the record, I will post images, but tomorrow.

Nice find!

Sjoelund

Nice find!

What do your 1989 and 1990 weigh?  Numista says 1.25g, SCWC says 1.53 g.

Some are still not measured!

So Numista is correct and SCWC incorrect?  Very confusing.

Here's a picture of a 1990 I found with coin roller damage. It not copper plated zinc.

rsirian1

So Numista is correct and SCWC incorrect?  Very confusing.

 

Here's a picture of a 1990 I found with coin roller damage. It not copper plated zinc.

At a certain time, I gave numista my measurements….. and 1.24 looks like one of mine, check the diameter and thickness to confirm?

And your 1986?  I don't understand how the bronze one and the copper plated zinc one with the same dimensions can have the same weight (as Idolenz said).  The plated one's weight should be about 80%.

A possibility were diameter and “thickness” could stay the same is if the bronze coin has a way deeper profile then the zinc copper one (decreasing the overall volume).

When you measure a coin with calipers they are usually set on the rim of the coin, the actual topography of the faces could be way lower for some extreme examples.

Image of my 1990 coin

rsirian1

And your 1986?  I don't understand how the bronze one and the copper plated zinc one with the same dimensions can have the same weight (as Idolenz said).  The plated one's weight should be about 80%.

Idolenz

A possibility were diameter and “thickness” could stay the same is if the bronze coin has a way deeper profile then the zinc copper one (decreasing the overall volume).

 

When you measure a coin with calipers they are usually set on the rim of the coin, the actual topography of the faces could be way lower for some extreme examples.

I measure the thickness over the full diameter of a coin, not just the rim……

Sorry for the delay, as promised above, here are pictures of my two 1990 cents.  Again both weight in at the 1.24g level and both look like copper pleated zinc to my eye.

Less light on the upper right image to make the date stand out.

The rim goes all around the coin, where have I said something about placing the caliper unsteadily on one edge?

Sjoelund

Idolenz

 

When you measure a coin with calipers they are usually set on the rim of the coin

I measure the thickness over the full diameter of a coin, not just the rim……

? How can that be understood differently?