Mystery Crock

My sister and I are puzzled. We've not seen a crock like this one before. It has a tin or metal removable tubular insert.There is also a wide metal or tin band around the crock. It is blue in color. The lid is cockery material as well as the outer crock. (see first photo) And it has a small hole in the bottom. (see third photo). It does not appear to be too old. It's interesting and would sure like one of you to tell me it's purpose. thanks from Mary