First impression was a tooth but not really sure. It is rounded on top as shown in the pic yet flat on bottom. I may open it up next weekend and take a look.
While installing a drain plug on my 8 3/4 I pulled out the large piece with a magnet (not the penny- :p ) it wasn't the only piece but by far the largest. How bad?
Doing it tomorrow......at least I was until reading your post. Do you think drilling will compromise the strength enough to merit the 1/8 plate? I am putting in 1/8 pipe plug.