On the one hand, it's pretty mundane. Milk goes in, up to three gallons at a time; vigorously turn the crank for fifteen minutes, and the cream comes out one spout while the skimmed milk comes out the other.
On the other hand, it's pretty darn cool. It is a home preparatory centrifuge. You crank it by hand, about 60 rpm, And the gearing takes the rotor to over 10,000 rpm. From my life in biology, I'm used to sample centrifuges--a sample is loaded into a bottle or tube; after spinning, the tube or bottle is removed, and the partitioned sample is decanted. You do one sample at a time. But preparatory centrifuges are magic; they can be continuously loaded and unloaded as they are spinning and separating. The magic is in the rotor, the bit that spins so fast.
Milk is continuously fed into the port on the top of the rotor and subjected to an intense gravitational field. Just as continuously, the cream is ejected from one escape port, on the left of the neck in the picture, and the milk escapes through the port lower down on the neck. Even cooler, the heart of the rotor is a series of "cones." These divide the volume of the rotor into a dozen stacked sections. This has the effect of taking a sample of milk and subjecting it to an extreme gravitational field once; then taking the upper portion of that, and subjecting it to an extreme gratiational field; then, taking the upper portion of that, and repeating over and over again. To get the same effect with a rotor with only a single compartment, the rotor would have to be meters in diameter. (Interestingly, the technology dates to the 1800's; before, "skim milk" was the result of letting milk stand for quite a while and then skimming the top layer off.)
Yummers. The skim milk has been mixed with whole milk, and is turning into a tomme as I write.