Over the years, I have seen a couple of AR-15A2 Government Models with black buffers. One was on my rifle, I thought maybe someone had replaced it, later on I saw a photo of an AR-15A2 GM disassembled and it had a black buffer as well.

The buffers were not plastic but appeared to be the standard aluminum buffers with a black finish rather than the gold color. Anybody know the story on these?