Numbers 2 (earllier) and 3 (later)...
Universal. The earlier types went with the tank-type cleaners, and the later model came with the Jet99. These were called "Self-cleaning, thread-picking" nozzles. They first appeared on the company's straight suction upright cleaners in 1919. The teeth were to designed to provide air flow, and also to prevent the nozzle from "sticking" to the rug.