Interesting find

Recently, a gentleman donated a number of objects he obtained as a student in 1955 working on the "St. Marks" dig in Florida, to the Chester Historical Society. The students where allowed to keep their surface finds.  Ray Decker was kind enough the examine the lot and while most of the bits where routine pottery fragments (some, plain, some impressed) he found one most interesting.  It has a very regular, almost machine like, square pattern. It seems to have a large radius compound curve, suggesting that it might have been part of a large vessel. The pattern is on the outside of the curve - inside is smooth.