Found a hollow sounding half?

[jim4silver]

Today I found a 1995 D half that seems light and sounds hollow. I through some halves into the dump pile and heard a weird sound. At first I thought maybe I missed a 40% or something. Then I found this coin. It is definitely not right. Anyone find anything like this before?

Jim

 

[Fruitbat]

A couple weeks ago I found half of one of these. What's the story behind these?