Odd Weight for a 1982 penny

How accurate is your scale? When was the last time you calibrated it? Can you take a picture of the coin on the scale?

 

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The guy said it is a calibrated scale where he works. We have a set up like this where I work. It's a 3 digit scale that is on a calibration schedule. The scale should be good, however, the repeatability of the test can be tricky, especially if the operator hasn't done many of these. The OP got range of 8.91-9.02 (hopefully he did more than 2 tests) and the spread might be from test variability. That's why I suggested he measure some copper Lincoln's as well as talk to a quality engineer. Many quality people have a solid statistical background and can help determine the right sample sizes and if there are statistically significant differences.

As @desertgem pointed out, there are additional areas of variability present, so that's why you need to measure more than one piece and not rely on theoretical calculations, especially when the compositions are very similar

 

Badthad has some interesting information in another thread about the transition year from copper to zinc that may be relevant...

 

What is the precision of the scale? How many test runs did you do? Where results consistent among other control specimens as compared to the subject coins? (Did you test other 1981 canadian cents and 1982 US cents to make sure you weren't running tests on an "odd" piece?) If you are trying for precise SG figure (more than one decimal place) are you isolating from drafts and compensating for temperature of the water? Where did you get composition specs for the Canadian cent? I know they are bronze but not the actual official composition percentage specs. Do you know that making up a melt it is very difficult to impossible to hit a planned bronze or brass composition to within a couple of percent since the tin or zinc in the alloy boils at a lower temperature than the copper melts. It isn't just a simple matter of adding the proper amount of each metal and melting them. Take too long to create the melt, or hold it molten too long and the whole time your zinc is boiling off. The actual composition of the melt is a moving target. If you can hit the target within 2% you're good.

This is curious because with the Canadian coin being bronze and US coin being brass, and the copper percentage probably being in theory about the same I assume, the densities should be as well. You are getting a measured value for the US cent between 8.91 and 9.02. The spec SG is 8.83. The measure values are higher than the spec value but the high value is still about just 2% high, the lower just 1%.

An XRF test would be illuminating. If the Canadian coin is actually bronze as it is supposed to be I would expect to see a reading for tin, possibly a significant reading. Tin was eliminated for the US cents in 1963 so any more than a hint of tin would be reason to question.

 

I’m not taking pictures on a scale. I’m not trying to convince anyone of anything. I’m gathering info. You are right, I should do more density tests. However, I was also hoping for new intel. Yes, I could have a coin that is both thin, but also has less zinc than what is standard.

 

I do like how you are wearing I Love my Wife shirt while displaying your collection. I may have to find me a shirt like that so I can wear it when I get mail call of a new coin maybe she wouldn't shake her head at me as much lol.

 

Look at Paddy's shirt a little closer!

 

Haha I had to zoom in to see that. Definitely going to find me one of those

 

Information is a two way street. We are trying to give you information but we want to learn about your coin as well, why it is what it is. The same as you, it's called sharing information.

 

And note what I said earlier about the difficulty of getting the alloy precise. That makes it believable that the copper percentage could be high and still be a "normal" coin.

 

Assuming I have a slightly thin Planchet 1982 copper penny yielding a weight of 2.82 grams. What is the value? I can't find any info on thin planchets. I don't think I will sell it, but I want to know how careful I should be with it.

 

Value would be one cent. The weight is only .17 grams out of tolerance, you aren't going to get much if any premium until you get to around .3 - .4 grams out of tolerance.