If you have any interest in Alabama pottery, you should know Joey Brackner and his (*fantastic, encyclopedic*) book, Alabama Folk Pottery.
I know Joey, so when I found these curious markers in a Walker County cemetery, I asked him what he thought. He says they were made by the Loyd family in Pine Springs, near Sulligent.
Sure enough, there’s a picture of a very similar marker in his book. The Loyds did register a US patent for stoneware tombstones in 1879, and they kept making these into the 1890s. They’re all salt glazed with cobalt decoration.