Go Suntour, it just looks better on older bikes. My drum brake behemoth weighs over a metric ton, its ridiculous, the rear wheel is about 6lbs on its own (assuming you can get the thing out).
filing back brazing is a slow and tedious process. It's possible it was pro built, but to reduce the cost the buyer asked for unfiled brazes. Many framebuilders brazes are far from pretty "straight from the torch"
It does seem crazy that someone, somewhere, at some point in time built this, but that it has all been lost in the annals of time, it's not even that old relatively speaking.
It's cool that it is still being ridden as intended, and enjoyed and I guess the heritage is irrelevant, but it would still be nice to know from whence it came.