This was the earliest stove we used. We also used coal cake stove, alcohol stove and electricity stove before gas appeared in our life. It was replaced when I was about 4 or 5 years old.
I can't recall all the details about it, so I called my Mom up and got a lot of information. My Mom asked to be the 2nd author of this series....
Coal balls look like this.
Burning a coal ball stove could create a lot of smoke and ashes.