Ok, scale is probably good. The possibilities I can think of that fit the known facts are: The coin left the Mint weighing between 2.95 and 3.04g, which would cause your scale to read 3.0g. The coin gained at least 0.35g in its rather rough lifetime. I can't think of anything that would cause a coin to gain that much weight other than plating. But that's clearly not the case. My (metaphorical!) money is on possibility #1: it was born that way.
Probably not. It would just come back "damaged" from any grading service. Maybe you could send it to CONECA and they might look at it for a reasonable amount of money or something. I'm intrigued by this weight mystery, but I don't think I'd even send it to CONECA if it were mine. I'd probably just throw it in a holder, label it, and keep it as a curiosity.
There were 1983 cents minted on 95% copper planchets but as others have pointed out there seems to be a lot of zinc showing. It is also known that overweight/underweight errors exist. Likely less rare than the copper planchet variety too. My guess is it's a weight error.
I'm just curious Sheila... are you hunting for planchet errors or are you hoarding copper cents and came across this one?
No, I am not hoarding anything. I just keep the ones I like and put the rest back into circulation. I am looking for any and all errors. Learning as I go along. I finally got a few books to help me out though. Our local book store does not carry the books I needed. I waited until the coin show came and I bought them there.
O oh man! I grew up watching he man and shera! I was always called that! Lol! Half pint is my other nick name because I am 4 foot 6 inches and change.