Fisher with vent holes in the top?

1979 / 80 Grandpa, '79 was the first year they bent the corners with a wrap around sheet for the stove body for the upcoming changes for 1980. They offered the new "Cathedral" arched top doors as an option. 1980 phased out the old style flat top, and only Cathedral was made thereafter. Notice no angle iron up the corners, yet it still has the old style flat top doors.
No doubt the owner raised it with the same pipes used for the convection tubes to make it higher for more comfortable loading.
All-Nighter brand had two tubes similar that went from the bottom where the air is coolest and out the step in the top like that. I'd imagine these tubes go out the back? Wherever their intake source is, an exterior manifold with a fan blowing through them would move a LOT of heat out of those tubes. Depending on their thickness, the downfall to the tubes was rotting out. As long as they're schedule 40 or 80 steel pipe, they should be fine. They look to be about 1/4" wall.

No idea who did it. Don't think it was factory, unless it was built for someone who worked there.........or the welder himself. Wouldn't be difficult to look pretty for someone with a mig. Stick takes practice. It would take a metal cutting hole saw, locally available to most anyone. I think Irwin makes them. I have a set from Mac Tools that I got for wood, but have used for cutting the hole in well casing below grade for pitless adapters. With oil and ran slow they cut a nice clean hole. A good welder, or one who does it for a living could weld it right up. You should be able to tell looking closely at the factory welds and compare the bead. If you know how to weld, you'll notice a different heat setting, or the weld "piled up" , or flatter. Spatter would be cleaned off on the stove top where it's very visable, so you can't go by how well other welds were cleaned up. The speed the rod was moving (distance between the "waves") would be different by someone else too. Keep in mind welding around the radius is going to look different than on a straight flat run. (mine would anyway) But if you live behind the arc long enough, it will get to be the same upside down!
So it could have been a welder's by trade, or someone who knew someone that welds a lot, or someone who took it back to the fabricator to have their buddy that worked there weld it for them. I'm sure there's a story behind it.