In the 1960s we had a Jersey/Guernsey cross, if her milk sat for 24 hours or more the top half of the gallon was cream, with the heaviest cream at the top. The cream on top was so thick we would pull it into the middle of the opening away from the sides of the jar and scoop it out. Then we had to scrape the cream off the scoop for the first couple ladles of cream.
My dad would get a heaping spoon full of the heavy cream for his coffee.
When that cow came fresh she would give 2 gallons per milking plus what the calf drank!
I love raw milk but the state of Oregon says raw milk is illegal to sell for human consumption, but what do they know? (They let Antifa practically take over Portland!)
Great explanation Cal.
We used a churn very similar to that one in the OP.
It probably had a square jar the mechanism sat on. The square jar causes more turbulence than a round jar so the butter churns faster.