The poplar one was from the other end of the same board as the previous one posted .I was glad it had some natural green coloring in it. I guess those black marks make it unique ? Made the red oak one at the same time and it too had some unusual markings .
The rings are cut out on a little machine called a Ringmaster Lathe. They fit together so good that only sanding is required . They can be sanded right on the RM or on a separate lathe . I sand mine on my little 12" Rikon mini lathe and a chuck is not required for that .