A barometric damper controls the draft pulling on the stove.. this is ESPECIALLY important with a non-airtight stove...
With a tight stove,, you can to some extent limit the air getting to the fire.. so if the draft changes during the day or overnight when nobody is around the stove to notice it is getting HOT, the stove can limit the excess air to the fire somewhat, reducing an overheat. With a non-airtight stove, the air leaks would allow way too much air to the fire, burn up all it's fuel too fast, probably overfire the stove, or many other much worse scenarios..so you need to control the draft. A manual pipe damper doesn't control draft, it adjusts airflow rates, and only to some extent.
With a barometric damper,, you can set the draft that the stove sees at say .07"wc... and from this maximum draft, you can control your air to your fire.. If the draft in the chimney changes drasticly,, the barometric damper will keep it at .07"wc, and the stove and the fire won't know that the wind outside is not blowing at 35knots, and the chimney is pulling .12"wc, which would surly overfire the stove and create a dangerous condition, even with a manual pipe damper..
For anthracite to burn well, and in some cases for it to burn at all, you need ALL the air getting into the stove to come through the coalbed from below, through the grates.. with some stoves, even a small amount of air leaking above the coal bed will steal too much air from the coal fire, and the fire suffers or goes out..
With a non-airtight stove,, and a manual pipe damper,, where do the excess combustion fumes, Carbon Monoxide, and smells go if the damper is closed too far? [or set for a very strong chimney draft] and the chimney draft drops drasticly [wind drops, temperature climbs, low pressure system/frontal passage].?.. Well the fire is going to slowly go out or burn lower,, but coal is very slow to react, so there could be a time period where there is positive pressure in the stove,, and fumes and CO are leaking out of the not-airtight stove body... and into your house...
So.,, get a Night Hawk [I think that is the brand] CO detector,, or another brand that has a DIGITALreadout, not just an alarm.. keep one in the room with the stove, and one near or in the bedrooms.. read them often, so you know what the normal readings are.. a false alarm is much better than NO alarm, and you don't wake up the next morning..
If I were to use a non-airtight coal burning stove,, I would NEVER run it without a barometric damper, and I'd probably not use a manual damper,, this would depend on just how controlable the air to the fire actually is..
If your stove has obvious areas that will leak air,, I'd get some furnace cement and carefully and neatly seal these joints.. You have a very nice stove, and you want to have if funtional and SAFE.. You might be able to create a draft with either a hot light bulb or a hair dryer in the stove,, and then use a candle or a cigarette as a smoke source [or a stick of incense] use the smoke to detect air being pulled into the stove around the doors, windows, and joints.. deal with them now, and enjoy your stove when the weather turns cold..
The houses that were typical when non-airtight and open hearth coal stoves were common were VERY drafty houses.. the windows didn't seal, there was no weather stripping or very primitive weather stripping. So the House breathed very well,, a non-airtight stove had lots of fresh air to feed the fire from.. But in today's tight houses, without proper care, prevention and precautions,, a non-airtigh coal stove could be dangerous... So please put safety on the top of your list..
A barometric damper must be between the chimney and the stove, nothing between the Baro and the chimney.. if a manual pipe damper is installed, it cannot be after the baro, it must be between the stove and the baro.