Paddyman...do you know what's White, Irish, and lays out in the backyard all night? (Paddy O'Furniture ) ...that one never gets old! Edit: I just read the thread about "Errors To Die For". Sorry, I just assumed you (like me) were Irish.
In the op it looks like a seam at the top of the D side just inside the rim. The image is taken at a slight angle so you can't see inside the rim at the bottom.