I have just purchased a rusty old No18 Oak Garland and I am restoring it. Just got the rust off of everything and put on some stove oil. My question is there is a piece on the back that runs up from the bottom to a vent in the piece and also three square holes at the top. Is there a piece missing? What is the function of this piece and these holes? Should they have some regulating piece to open and close them?