This penny weighs 2.7 grams. Could someone tell me if its zinc or copper? To my understanding 2.5 is zinc and 3.1 is copper.

It would be Copper plated Zinc. Coins have a slight plus or minus difference in weight varience.. 2.7 is just a little bit more for the correct weight of a Zinc. And obviously 1983 is the second year of the Copper plated zinc cent.

the only year you would have to worry about the difference is in 1982 because they switched the composition halfway through the year

This is not true. A number of 1983 cents have been discovered on copper planchets. And a few later dates than that as well. One of the off metal copper cents was a little light (2.9 or so). I am not saying this one is copper, but it could be copper on a thinly rolled planchet. I would get a much more exact scale to the hundredths.

As Paddyman said it is just a little off for being within tolerance for a zinc cent, but way off tolerance for being copper. A weight to two decimal places would be helpful.

A copper alloy cent is 3.11 Plus/or minus 0.13grams so 2.98grams to 3.24 grams ( you have to have a scale which will weigh the 2 decimal places) The copper coated zinc cents is 2.50 plus or minus 0.10 grams or 2.40-2.60 grams. In between 2.60 - 2.98 , you might need specialized instruments such as XRF to test, and 99.99% will not be what a person wants. Put it away for 10 years and your cell phone may have a free app. Jim

It was my understanding, that even though lighter, the zinc cents had the same +/- .13 tolerance. Has this been updated to .10? Thank you.

Early internet references said it was the same, but searching later pops up the newer one. I figured the tolerances would be in % , so the same percentage when used with the 2.5g came out close to .10 g (.1025 as I recall), so I just accepted it. If anyone else does the math, thats Good. Jim