Taken during World Pinhole Day up in Brattleboro VT. This is Brattleboro's version of the Flat Iron building... or at least a pinhole cameras take on it. The building is a storage barn for a sheet metal shop.
Thank you Eddie and Miles.
As to posterization, there is none to be seen on my monitor or on the print. So I have to assume that it is your monitor that is picking this up.