1976 Penny Wrong Planchet Error? Any experts out there?

[jtryka]

So today I was rolling up some pennies from my copper penny picher, and I came across a very strange 1976 cent which was very light and a lot thinner than the usual cent. From appearance, it looks about the same as any other penny, just that it's thinner. When I dropped it on the table, it sounded funny too, almost like a Canadian penny sounds. Someone scratched it all up as well, likely because it sounded wierd they wanted to check it it was copper and it appears to be,

 

So I was thinking maybe this was struck on a wrong planchet, but I'm not sure what other similar foreign coins the Philadelphia mint might have been striking in 1976 allowing for this error to occur. So any thoughts would be appreciated.

 

I've attached a couple photos, but they don't really show the real odd stuff like the lighter weight and wierd sound.

 

Thanks for any help or insights!

[WoodenJefferson]

I have no explanation that would be concise.

 

I have seen thinned planchets before, but copper, no.

 

The rim on the obverse is really not quite right, strange.

[jtryka]

Well, I did a little research, and the Mint did make 1-centavo coins for El Salvador in 1973 which were only 2.5g and made of 95% copper and 5% zinc, so that's one possibility. They also minted proof Liberia cents in 1976 which were the same composition and 2.59g. Philippines 5-centimos of 1976 were minted of 2.5g 60% copper and 40% zinc.

[e1cnr]

do you have a very accurate scale? weight would be helpful

 

I have seen coins that had been stripped some being used as metal source in electroplating projects - some detail is lost but not alot.

 

I have seen cents that look gray because they did not have the copper plate and you just see the zinc.

 

 

[jtryka]

No, unfortunately I don't have a scale that goes down that far. This is a 1976 cent, so there should be no zinc later, though it is possible that it's been part of an electroplating experiment, though that would take a uniform layer of metal, while this coin exhibits strike weakness on the reverse around the motto and "United States" suggesting an underweight planchet.

[RWB]

Make your own beam balance.

 

1. Take a straight stick, and tie a string to each end and one in the middle.

2. Attach the each of the end strings to a bottle cap so the cap is positioned like a small pan.

3. Put a pre-1982 cent in each cap. Cents should be as close to identical as you can make them.

4. Lift the stick slowly by the middle string until the caps are just off the table top.

5. Move the center string along the stick until both caps hang at equal heights from the table.

6. Lower the stick slightly until the caps lightly touch the table, and remove one of the coins. Replace with the 1976 cent.

7. Lift gently. If the 1976 is too light, the normal coin end of the stick will stay on the table and the 1976 coin end will lift off the table. Opposite effect if the 1976 coin is heavy.

 

Done carefully, this is accurate to 0.01 gram.

 

[Conder101]

Your balance may be able to detect a difference of .01 grams but since the cents, due to tolerances, can vary as much as .2 grams all you can really determine is whether the test coin is heavier or lighter than the balance coin. It really can't tell how it compares to the standard weight and tolerance

[jtryka]

Ok, I will find an appropriate scale and let you all know how it turns out.

[RWB]

The stick contraption is not a scale - it's a balance. A balance compares known to unknown, so it will show if the 1976 coin is lighter or heavier than a presumably normal coin of the same composition. (This was how the US. Mint measured weight in most cases.)

[Conder101]

You'll notice I called it a balance. The problem is it it would compare the unknown 1976 cent against an assumed normal "known" 1976 that could weigh anywhere from 3.2 to 3.0 grams. Even if your known was exactly on the official weight, an unknown that weighed 3.05 would show as light, but still be within tolerance.

 

A balance is great for telling you if one thing is heavier than another but not by how much and it doesn't tell anything about actual weight unless you have a test weight of a known amount.

[Rigo-migration]

Good info. I know I learned a lot.

[jesbroken]

I thought that Jeff said that it was definitely lighter and that it appears in the photo to be definiitely thinner. That should save a lot of time making a balance beam.

Jim

[jtryka]

Ok, I did an improvised balance, since RWB's sounded too complicated for me, so I took an unused penny 2x2 and balanced it on the ridge of a pencil and got 2 copper cents to balance, then tried it with this cent, and it was clearly and heavily outweighed by the normal copper cent. Then I tried the same trick with a zinc cent on the other side and it was very close, but the 1976 cent was a little heavier. The spec for the copper cent is 3.11g, and for the zinc cent is 2.5g, so this one is much close to the 2.5g. I know this isn't definitive, but it suggests this cent is not within tolerance for a 3.11g copper cent.

[RWB]

Good improvisation, though! Now you probably know a little more than before. Just keep investigating.

[jtryka]

I had it weighed at a local show yesterday, and it's 2.5 grams, so much lower than the 3.11 grams of a normal copper cent.