A single plate stove, suitable for students, singles and generally anyone with a minimal kitchen.
Originally, these had only the naked wire, wound up helicoidally (I detest the american way of calling it a spiral - spiral is a flat figure), laid zigzag way in grooves of a ceramic insulator, and getting visibly red hot when turned on. The thing was outright dangerous. I remember we had one of those when I was a kid, it was used mostly to make coffee, because it was fast, even though the "plate" was larger than the half liter pot they used.
The next one was what I had as a student, and that one served us as the only other stove (apart from microwave) until we moved into our house. So that's about 1976 to 1993. That one had the iron plate above, and even had a thermostat.