Manual coffee grinders have been around since Nicholas Book from England invented them in the late 1600s. The design of those early coffee grinders looked a lot like the Coffee grinder you see in Animal Crossing: coffee drinkers put beans at the top of the machine and turned a crank which fed the beans through a burr (a round wheel with sharp blades). When you wanted to make coffee, you could open a drawer at the bottom of the machine and ground coffee would magically appear.
I recently read Laura Ingalls Wilder’s Little House series with my daughter, and there are scenes where Laura described how during a hard winter the Ingalls family used their coffee grinder to grind flour out of wheat. They would have used a coffee grinder that looked a lot like this one.
Believe it or not, Nintendo actually sells Brewster's coffee grinder on their Web site. I thought for sure that this would be a limited time item, but as of this writing it's still available. It even has engravings with Brewster's The Roost logo, the Animal Crossing leaf logo, and Brewster's advice to "Drink up...and Enjoy".