1959 D Penny underweight

I have a 1959 d Penny that sounded different so I weighed it and it is 2.43g. Seems like most under weight coins are chemical errors over time, my question is how do you tell if it’s a planchet error or chemical? It is not silver and non magnetic. Thanks.

22% light wouldn't be caused by either since the surface does not look severely attacked. You measured the weight of other pennies and they were correct? Can you post a picture of the edge and measure the thickness?

I wasnt very successful at measuring. Here’s a photo of it in the middle of a 1946 Penny and a 1968 Penny. I double checked the scale and it seems to be weighing the other pennys correctly. maybe this is a new Penny faked to be a 1959 Coated?

N#42

Thanks for the pictures.  A real measurement of the thickness and diameter would be nice but it appears it's thinner than a normal 1.4mm penny (maybe 1.1mm?) and the same diameter of 19mm.

It's very unlikely it's a manipulated copper plated zinc coin (2.5g, 1.4mm). There's no evidence of that, there's no real incentive to do that and it still wouldn't explain why it's thinner. 

This is pure speculation on my part but maybe a blank of the wrong type got mixed into the right blanks.  At the time in 1959 the US Mint was making coins for other countries.  One was for the South Korean government. It's this coin: N#5952 Same composition (95% copper, 5% zinc), same diameter (19.1mm) but thinner (1.1mm) and lighter (2.46g) than a US penny. Seems to match yours.  One negative, they were made at the Philadelphia mint, not the Denver mint.

I don't know how to prove or disprove it. Maybe another member will chime in.

Thank you so much for your time on this! I really appreciate it.