It appears that both the lid and air intake adjuster plate are in the pile of parts in the stove along with boot rails that use the square holes to mount on each side.
The flat plate covers the hole in front, and curls up under the door to close the large opening under door, adjusting how much air goes in to feed fire. This is like the throttle on an engine.
The grate inside is probably for coal since box stoves like this were sometimes made for wood or coal.
Do not open the upper rotating secondary air too far with wood. This allows indoor air to rush up the chimney, cooling it with excessive indoor air.
With coal, it is only cracked to allow oxygen above fire to ignite coal gas.
Once a coal fire is established, the upper secondary air intake can be opened to allow indoor air up the chimney to slow draft. It is then called a “check” damper, because it checks, or slows draft by cooling the exhaust gases. Don’t do that with wood, it cools chimney flue too much forming creosote.
When you understand what makes a stove work, you can figure out what different openings into the firebox are, and what they will do.
All stoves work on this principal; Hot exhaust gases rising up the chimney causes a low pressure area, or vacuum in the chimney flue, pipe, and stove. This is measured as draft. This allows the higher atmospheric air pressure outside of the stove and venting system to PUSH into any opening it can. This feeds the fire oxygen.
Wood uses air from any direction it can get it. Coal requires lots of oxygen up through it to make it burn. The chimney is what makes the stove work since air will not move into the box to feed the fire oxygen without the proper draft.
Since the outlet opening is attached to chimney, you can see how opening the upper air too far allows indoor air to rush up the vacuum of the flue without doing the fire any good.
