Just a nice old wooden foundry jar mold with a good patina. The half-bottle form is attached to its original mount, with the letter and numbers I assume referring to the bottle or jar type (and there are more handwritten notations on the back side.) A loop at some point was added at the top for easy hanging. Great in the kitchen or pantry--looks like a mason jar to me!
Very good vintage condition, with just the right amount of wear.