ceramic oil burning heater

I was doing a ride along recently with a seasoned licensed home inspector. In the basement, we noticed a beautiful cast iron stove. “Oh look a wood burning stove!” i said…and it was blue. not large…just an unassuming little thing. The seasoned inspector thought so too…then he realized it had been installed to replace an old, whole house oil furnace.
there was no grate inside the little door, just a little pot of some sort for burning the oil. it was ducted to the whole house. amazing. the old furnace had been mostly removed with some parts remaining and that was the give away for the seasoned inspector i was with.

nothing i read about in the manuals or books showed me anything like that!