That is an interesting jug. One thing about the debossing nags at me. Somehow, this doesn't appear to be an impression on damp clay in the manner these stoneware items are typically marked. Other debossing I've seen has been filled in, sometimes even obscured, by slip applied over a stamp.
Are the letters cut into the body? . . . That is, is the dark slip on the surface of the jug cut through after the jug was fired? That would be a daunting task, but not impossible, I imagine.