I had a DO thrift store find. I stripped it in a lye tank for several days. Scrubbed it and it turned out clean. Then I seasoned it with crisco. At completion of the seasoning process, there appeared a silverish spot on the bottom inside as seen in the picture. After having restored many pieces prior with no such spotting occurring, I decided to strip it again and repeat the process - ending with the same type spot in the same place! I have no idea what the issue is but am confident that you more seasoned cast iron restorers will have some useful thoughts and suggestions. Much TIA!!