Here are a couple of Demijohns in my collection that I picked up real cheap. They are the only two I have kept, but I am now looking for more. The smaller one is about 16 inches tall.
They both have sharp pontil marks on the base and each has a small crack going out from the pontil. I picked up the smaller one at the TriState clubs show in Nov (thats PA, MD and Del). The show is in Elkton Md in NE Maryland. I paid $5 for it. I picked up the bigger one at a weekly auction for $3. I did get two small junk items with it that I have since sold for $4. The crack on the smaller one isn't very big, but on the bigger one it goes a few inches up the side of the bottle. Still, they both are very crude and look great (to me) on the shelf.