I've been doing a little thinking about the design of my Keystoker vs. some of the pictures and postings of other Keystoker owners here.
If you look at the design of my stove, the top door is quite a bit lower than the newer model, the vent for the hot air is very different, and the 'guts' of the firebox appear to be significantly different.
My stove has an angular roof area above the fire with two steel tubes about 3" diameter leading up into a flat heat exchanger area surrounded by the air from the fan. The gasses then pass across this exchanger area and down the sides of the stove and exit around the ashpan level of the stove.
Futhermore, the entire firebox assembly is wrapped with the outside shell of the stove, so between the stoker and the outside stove shell there is 4 layers of steel. I can't even begin to estimate how heavy my stove is, but 500# fully assembled is no stretch. It's a heavy PIG!
WNY Dave mentions that he sees almost 500F on the side of his stove when it's really cranking. I've yet to get mine above hand warm, yet the hot air coming from the front of the stove is HOT! My exhaust gas temps have not been above 180F or so no matter what the firing rate.
Now, while it may seem that I have a very efficient stove from a heat extraction standpoint, I also have a very efficient fly ash collector. That upper heat exchanger area on my stove was fully packed with fly ash, which between vacuuming, compressed air, and moving the stove 400 miles on it's side, knocked piles of it loose. This will be a high maintenance area and require some specialized brushes, etc. to keep it clean and efficient.
I talked to Don at Keystoker about it a little, but we did not get into any detail about it. If any of you other Keystoker owners wants to take some pics of your stove guts, I'd appreciate it. I'll show you mine if you show me yours ! I just find the design of this stove fascinating in the amout of welding and fabrication it required.