A rare unit: a gravity furnace. This one burned gas since Day 1 (the 40s) and was still
in good shape when the homeowner had us remove it. There was no fan, the heat from the fire rose into the home by gravity. The cold air fell back into the furnace in the huge ducts into each side. It did have a humidifier! But cooling was not possible.
We don't very often replace a 50 year old furnace with one of the same brand. Back then there were hundreds of small furnace companies. Now there are just a few. But in this house, a modern American-Standard Freedom 78 replaced the antique American-Standard furnace. And he has central cooling!