That is a double walled clay bowl, and the interior of the facing side was coated somehow to reveal a picture
as the bowl colors. From what I can tell it's a pastoral scene with three maidens approaching a pond while
carrying baskets. It's still developing, but I think it will be blurry even after it colors-in. Here's a close-up.
I bought this pipe around 1966 or 67. The only marking is on the shank:
Manhattan. If anyone knows who made
it I'd like to know.