I have a 1963 Kenmore 70/700 which is about as bad.
That said, I've learned some things about the older more vintage machines from having used some recently. I've used 1980s Kenmores for so long, which have less accessible tub rings, taller baskets, and longer drain periods, that I'd forgotten what used to happen in these older models.
Suds were more common in vintage detergents than today. What happens in these older BDs is that the suds created from wash agitation does not get as much chance to dissipate with a two minute neutral drain as it does in a four minute drain in the later machines. This seems to make a huge difference when all else is held equal with my various machines. Couple that with vigorous agitation from a straight vane or Roto-Swirl and the wash water can get rather foamy. Then, the machine goes into spin maybe 15-20 seconds after the tub empties (like drinking a soda or beer just after it was poured, before the foam drops off). The spin then foams up the suds even more, and it works its way up the sides of the outer tub and basket, then starts flying out over the top of the basket. The wind from the spinning clothes and the agitator fins then blows the suds up onto the tub ring, which is open and easily accessible in the older BDs. These suds then dry out, and reconstitute themselves so to speak. Over many years, if not cleaned off, the dried up suds build up to resemble over-spilled detergent.
So, I think that built-up "detergent" on Wigwagster's tub ring is really dried up old wash water with all the suspended soils, etc in it.
That is probably how the 1970 500 you saw got all that stuff apparently flung everywhere, because it probably was flung, but just by the machine itself instead of the user(s). Certainly though, the way a lot of us used to dispense powdered detergent can get fresh detergent on the tub ring as well.
Incidentally, I've seen a number of posts on here where people complain that Whirlpool did a lousy job of aiming the spray rinse water, as a lot of it ends up going behind the basket instead of into it, and thus on the laundry load. There is a reason for this - the spray rinse not only rinses the load, but it is intended to rinse the sides of the spinning basket, to reduce the "climb" progression of suds.
Gordon