Vintage stoneware butter crock

This is a vintage stoneware butter crock, specifically a Rex Johncox butter crock from Onsted, Michigan. It's designed for storing butter, keeping it fresh and spreadable at room temperature. The crock is made of stoneware, and it features the "Rex Johncox" brand name with "FOR BUTTER ONLY" printed on it. The design is inspired by classic crock designs, which block out air to prevent spoiling.
Butter crocks, also known as butter bells, use a water seal method to keep butter fresh. The butter is packed into the lid, which is then inverted into a base filled with water. The water creates an airtight seal, preventing the butter from spoiling and keeping it soft. This method is preferred over traditional butter dishes because it keeps the butter at a more consistent temperature and prevents it from melting or hardening.