I came across a 1968-D US Kennedy half dollar
which should be %40 silver with 11.5g in weight.
This coin has 11.29g weight, so I decided to analyse its composition, and I found that this coin is made up with 79.34 percent silver and the rest is copper!!!
With this % of silver it's weight should be around 12.5g, but it's weight is about vopper- nickle one!!!
May I have your suggestions?