A lot of the time I just use a 6011 on my tombstone 60% of the "big stuff" I work on. But, I have been studying my equipment, particularly items made by Armstrong Ag. Most of that equipment is 1/2" or thicker and if you look at welds at any given location, it looks like they melted a wax stick in it. It's smooth, deep, and there is no "stacked dime" appearance. I'm not so concerned with how it looks as how it holds. It's stout and has very little spatter.

What kind of welding is this?

Could be submerged arc welding (SAW) from the description.

Being ag equipment, I would guess MIG, possibly robotic. Could also just be the finish. If it is powder coated, that tends to cover up the weld pretty well.

ETA: Most production welding is going to be MIG, which is more than capable of welding 1/2". Stick welding would be way too costly to clean up after and overall more inefficient due to have change rods so often.

Maybe done with what are referred to as "jet rods", E7024. Often used in fabrication because you can quickly lay down a lot of metal and the resulting weld beads are relatively smooth and clean. With them you drag the rod straight along the surface with no zig zagging or other motions, contributing to a smoother weld bead. The only positions they are intended for are horizontal and flat, so you need to be able to position your work accordingly.

I used to do summer work in a yard that made work barges (large pontoons) and they were welded up with jet rods. Even my welding looked pretty good when using them and was actually fun at times.

Hard to tell without a picture, but based on the description, could be submerged arc, assuming the weeks is a pretty significant size (1/2" is probably the minimum). Otherwise I agree with the poster above me.