You also have to consider that your stove running at 350-400deg will be putting out more heat and using more coal than my stove will at the same temp, due to the greater surface area of steel absorbing and radiating heat. We are talking about around 150 lb of extra steel your stove has.
12,500 BTU per lb. X 100 lb. in 24 hr.
12,500 X 100 = 1250,000 divided by 24 = 52,083 BTU per hr max at 100% efficiency of burn and 100% efficiency of stove.
Lets not take into account efficiency of burn, and say the stove is 95% efficient. That's 49,479 BTU per hr. for 24 hr. you will burn 100 lb. of coal.
Using that logic, we can see, my previous estimates were wrong, using 65 lb. of coal in the Vigilant wasn't producing 50,000 BTU per hr. and to max out the Baker it would take a lot more than 100 lb. of coal.
I guess the big question now is, how many BTU do you need, and are willing to pay for?
You could now take the known or estimated max BTU rating of the stove and work the equation to find out how many lb's. the stove is capable of burning in 24 hr. and say cut that in half or 2/3 and if that is more than you are willing to burn, the stove is too big.
The first winter I stayed in my current house, I heated the area we spent the most time in with only one 25,000 BTU kerosene heater. It didn't heat the house but that was all I was willing to pay for.
To sum up all my thoughts on the matter I think that you can expect most hand fired coal stoves, old or new to run at around 90% efficient. Most manufactures have there stoves tested and rated in BTU's. Even though Baker doesn't state their BTU ratings, they know it. That is how they can rate them for a specific sq ft. Different coals are tested and rated for specific BTU per ton or lb. With all this known info. we can determine the performance of any specific coal and stove combo. under controlled draft conditions, that we can manipulate with baros, or extended chimneys.
The wild card is how much heat the area we are trying to heat will need, to stay at a desired temp.
So how can we say this or that is too much or too little coal burnt, without saying it in the context of how much heat we are producing.